Disable work queue before enqueue to prevent work queue dequeue
from running in between enqueues. Move queue_task_test from
flaky test. Ran 100 iterations without failure.

Change-Id: I75f4ba31151604e540a558039dbd8f6793ec3c30
Merge "Disable work queue before enqueue to prevent work queue dequeue from running in between enqueues. Move queue_task_test from flaky test. Ran 100 iterations without failure."