Fixed wait skipped after 1st step of task

The first step of a generator type task is executed by the start
method and subsequent steps are executed by run_to_completion.
The TaskRunner skips the wait between the first step and second
step.
Added the sleep between transition from first step to second step.
Updated corresponding unit tests.

Change-Id: Iff30073ea0c060c6e2c89d7d9df8d0d03e816455
Closes-Bug: #1218187
Merge "Fixed wait skipped after 1st step of task"