[Changed] task to only start if the taskStart function returns true.
[Changed] task to only end if the taskEnd function returns true.
[Added] default return value can now be set when using
callFunctionIfNotNil function from the task module. The default return
value will be used if the function is nil.

Change-Id: I80d9a812228f9d6d94dd6be023db65442e52e47d
Merge "[Changed] task to only start if the taskStart function returns true. [Changed] task to only end if the taskEnd function returns true. [Added] default return value can now be set when using callFunctionIfNotNil function from the task module. The default return value will be used if the function is nil." into unstable