Optimize timers for publisher lists

[NejcZdovc]

When users disable rewards we don't clear the interval. This means that publisher list will be downloaded next time even if rewards are off. This is because we don't check if rewards enabled on timers. This is not a problem for users that never enabled rewards/clean profiles.

[kjozwiak]

Verification PASSED on macOS 10.15.4 x64 using the following build:

Brave | 1.8.85 Chromium: 81.0.4044.122 (Official Build) (64-bit)
-- | --
Revision | 44f4233f08910d83b146130c1938256a2e05b136-refs/branch-heads/4044@{#963}
OS | macOS Version 10.15.4 (Build 19E287)

• enabled rewards via the rewards panel and ensured that the publisher list was downloaded.
• disabled rewards via brave://rewards and closed Brave
• edited server_publisher_list_stamp under preferences and moved it back ~3 days
• restarted the browser several times and ensured that the publisher list isn't being downloaded
• enabled rewards and ensured that the publisher list was downloaded without any issues

Example of publisher list being downloaded after enabling rewards:

[ RESPONSE - OnDownload ]
> time: 1588040094
> result: Success
> http code: 200
> response: Publisher list
> headers accept-ranges: bytes
> headers access-control-allow-headers: Origin, X-Requested-With, Content-Type, Accept, Authorization
> headers access-control-allow-methods: GET
> headers access-control-allow-origin: https://rewards.bravesoftware.com
> headers access-control-request-method: GET
> headers age: 1561
> headers cache-control: max-age=3600, public
> headers content-encoding: gzip
> headers content-length: 19006799
> headers content-type: application/json; charset=utf-8
> headers date: Tue, 28 Apr 2020 02:14:53 GMT
> headers etag: W/"cd3c678094a8b205d71bd20eb1477483"
> headers server: Cowboy
> headers status: 200
> headers strict-transport-security: max-age=31536000; includeSubDomains
> headers vary: Accept-Encoding
> headers via: 1.1 varnish
> headers x-cache: HIT
> headers x-cache-hits: 0
> headers x-frame-options: deny
> headers x-request-id: 0b9c3bc2-ee67-401d-8e80-d96ae1f129c8
> headers x-runtime: 2.940268
> headers x-served-by: cache-yyz4527-YYZ
[ END RESPONSE ]

Verification passed on

Brave	1.8.85 Chromium: 81.0.4044.122 (Official Build) (64-bit)
Revision	44f4233f08910d83b146130c1938256a2e05b136-refs/branch-heads/4044@{#963}
OS	Windows 10 OS Version 1803 (Build 17134.1006)

• enabled rewards via the rewards panel and ensured that the publisher list was downloaded.
• disabled rewards via brave://rewards and closed Brave
• edited server_publisher_list_stamp under preferences and moved it back ~3 days
• restarted the browser several times and ensured that the publisher list isn't being downloaded
• enabled rewards and ensured that the publisher list was downloaded without any issues

Example of publisher list being downloaded after enabling rewards:

[ RESPONSE - OnDownload ]
> time: 1588073906
> result: Success
> http code: 200
> response: Publisher list
> headers accept-ranges: bytes
> headers access-control-allow-headers: Origin, X-Requested-With, Content-Type, Accept, Authorization
> headers access-control-allow-methods: GET
> headers access-control-allow-origin: https://rewards.bravesoftware.com
> headers access-control-request-method: GET
> headers age: 358
> headers cache-control: max-age=3600, public
> headers content-encoding: gzip
> headers content-length: 19033260
> headers content-type: application/json; charset=utf-8
> headers date: Tue, 28 Apr 2020 11:34:35 GMT
> headers etag: W/"badde5f9b5a50b7a9ae683a56cb877d5"
> headers server: Cowboy
> headers status: 200
> headers vary: Accept-Encoding
> headers via: 1.1 varnish
> headers x-cache: HIT
> headers x-cache-hits: 30
> headers x-frame-options: deny
> headers x-request-id: 6cf80531-c397-45e4-b7f9-7428a3cb3d44
> headers x-runtime: 2.077662
> headers x-served-by: cache-bom18226-BOM
[ END RESPONSE ]

Verification passed on

Brave	1.8.85 Chromium: 81.0.4044.122 (Official Build) (64-bit)
Revision	44f4233f08910d83b146130c1938256a2e05b136-refs/branch-heads/4044@{#963}
OS	Ubuntu 18.04 LTS

• enabled rewards via the rewards panel and ensured that the publisher list was downloaded.
• disabled rewards via brave://rewards and closed Brave
• edited server_publisher_list_stamp under preferences and moved it back ~3 days
• restarted the browser several times and ensured that the publisher list isn't being downloaded
• enabled rewards and ensured that the publisher list was downloaded without any issues

Example of publisher list being downloaded after enabling rewards:

[ RESPONSE - OnDownload ]
> time: 1588097593
> result: Success
> http code: 200
> response: Publisher list
> headers accept-ranges: bytes
> headers access-control-allow-headers: Origin, X-Requested-With, Content-Type, Accept, Authorization
> headers access-control-allow-methods: GET
> headers access-control-allow-origin: https://rewards.bravesoftware.com
> headers access-control-request-method: GET
> headers age: 3130
> headers cache-control: max-age=3600, public
> headers content-encoding: gzip
> headers content-length: 19042981
> headers content-type: application/json; charset=utf-8
> headers date: Tue, 28 Apr 2020 18:13:10 GMT
> headers etag: W/"f3924eb0fef1f593895bbd17ec4ebcf0"
> headers server: Cowboy
> headers status: 200
> headers strict-transport-security: max-age=31536000; includeSubDomains
> headers vary: Accept-Encoding
> headers via: 1.1 varnish
> headers x-cache: HIT
> headers x-cache-hits: 0
> headers x-frame-options: deny
> headers x-request-id: b0c3523c-0ba1-47e7-8b31-4b14721d7826
> headers x-runtime: 3.037914
> headers x-served-by: cache-hhn4054-HHN
[ END RESPONSE ]