PLATFORM-75 Make TaskRunner aware of the task ID

For longer-running tasks, a timeout somewhere between application/dev
boxes and the celery workers can cause the task status to become
"failed" when it could simply be running longer. Passing the task ID
along to the runner will enable it to communicate back to Flower that
the task actually did complete successfully.
PLATFORM-75 Notify Flower when a task completes

In case Celery times out, ping out to Flower to record the actual result
of the task.
PLATFORM-75 Use GuzzleHttp for REST calls

An easy-to-use/robust HTTP client will be useful at the platform moves
to a service oriented architecture. Use GuzzleHttp for the Flower
long-task pingback.
Merge pull request #3751 from Wikia/jobqueue-migration-taskid

Make tasks aware of their own ID