Fixes 1043: Modifies snap to allow for removal of disabled tasks

[tjmcs]

Fixes #1043

Summary of changes:

• Modified conditional statement in scheduler/task.go to allow for removal of both stopped and disabled tasks

Testing done:

• started snapd and checked to make sure the mock plugins autoloaded
• created a task that utilized the mock plugins
• unloaded the mock collector plugins
• checked to make sure that the task entered a disabled state
• removed the disabled task

here's the output of the terminal session from the point where I created the task through to the point where the task was removed:

$ snapctl -u "https://127.0.0.1:12345" --insecure task create -t examples/tasks/mock-file.json
Using task manifest to create task
Task created
ID: a61d2366-402d-475c-b169-49fc1d6cd13e
Name: Task-a61d2366-402d-475c-b169-49fc1d6cd13e
State: Running

$ snapctl -u "https://127.0.0.1:12345" --insecure plugin unload collector:mock:1
Plugin unloaded
Name: mock
Version: 1
Type: collector

$ snapctl -u "https://127.0.0.1:12345" --insecure plugin unload collector:mock:2
Plugin unloaded
Name: mock
Version: 2
Type: collector

$ snapctl -u "https://127.0.0.1:12345" --insecure task list
ID                   NAME                        STATE       HIT     MISS    FAIL    CREATED         LAST FAILURE
a61d2366-402d-475c-b169-49fc1d6cd13e     Task-a61d2366-402d-475c-b169-49fc1d6cd13e   Running     19      0   9   11:57AM 7-14-2016   Metric not found: /intel/mock/*/baz

$ snapctl -u "https://127.0.0.1:12345" --insecure task list
ID                   NAME                        STATE       HIT     MISS    FAIL    CREATED         LAST FAILURE
a61d2366-402d-475c-b169-49fc1d6cd13e     Task-a61d2366-402d-475c-b169-49fc1d6cd13e   Disabled    20      0   10      11:57AM 7-14-2016   Metric not found: /intel/mock/*/baz

$ snapctl -u "https://127.0.0.1:12345" --insecure task remove a61d2366-402d-475c-b169-49fc1d6cd13e
Task removed:
ID: a61d2366-402d-475c-b169-49fc1d6cd13e

$ snapctl -u "https://127.0.0.1:12345" --insecure task list
ID   NAME    STATE   HIT     MISS    FAIL    CREATED     LAST FAILURE

$

@intelsdi-x/snap-maintainers

[IRCody]

LGTM