Ads not enabled by default when joining Rewards from panel

[LaurenWags]

Description

When joining Rewards from panel, Ads are not enabled. However, if you join Rewards from brave://rewards page, Ads are enabled.

Steps to Reproduce

1. Clean profile, install 0.65.67 nightly build
2. Click on BAT logo and join rewards from Panel.
3. Look for ads related files in profile directory, there are none.
4. Navigate to brave://rewards, see that Ads are toggled off.

Actual result:

Ads are toggled off.

Expected result:

Ads should be on.

Reproduces how often:

easily

Brave version (brave://version info)

Brave	0.65.67 Chromium: 74.0.3729.75 (Official Build) nightly(64-bit)
Revision	fdb7915642fef8cf997beac2554709d148e3c187-refs/branch-heads/3729@{#754}
OS	Mac OS X

Version/Channel Information:

• Can you reproduce this issue with the current release? n/a
• Can you reproduce this issue with the beta channel? no
• Can you reproduce this issue with the dev channel? unsure
• Can you reproduce this issue with the nightly channel? yes

Other Additional Information:

• Does the issue resolve itself when disabling Brave Shields? n/a
• Does the issue resolve itself when disabling Brave Rewards? n/a
• Is the issue reproducible on the latest version of Chrome? n/a

Miscellaneous Information:

If you repeat STR but join from brave://rewards, then Ads are toggled on.

cc @brave/legacy_qa

[LaurenWags]

Verified passed with

Brave	0.63.46 Chromium: 74.0.3729.91 (Official Build) (64-bit)
Revision	03844ed83e02b8add3f4b9cb859a7108d55b2e4d-refs/branch-heads/3729@{#860}
OS	Mac OS X

• Verified test plan from Fix Ads enabled when joining Rewards via panel brave-core#2266

Verification PASSED on macOS 10.14.14 x64 using the following build:

Brave	0.63.46 Chromium: 74.0.3729.91 (Official Build) (64-bit)
Revision	03844ed83e02b8add3f4b9cb859a7108d55b2e4d-refs/branch-heads/3729@{#860}
OS	Mac OS X

• Went through the test plan outlined under Fix Ads enabled when joining Rewards via panel brave-core#2266

Verification passed on

Brave	0.63.46 Chromium: 74.0.3729.91 (Official Build) (64-bit)
Revision	03844ed83e02b8add3f4b9cb859a7108d55b2e4d-refs/branch-heads/3729@{#860}
OS	Windows 10 OS Build 17134.523

• Verified test plan from Fix Ads enabled when joining Rewards via panel brave-core#2266

Verification passed on

Brave	0.63.46 Chromium: 74.0.3729.91 (Official Build) (64-bit)
Revision	03844ed83e02b8add3f4b9cb859a7108d55b2e4d-refs/branch-heads/3729@{#860}
OS	Linux

• Verified test plan from Fix Ads enabled when joining Rewards via panel brave-core#2266