Add AsyncTaskUtil for call log actions.

+ Factors out async tasks from Call Detail activity, so that in the
near future it can be invoked from the call log directly.
+ Create listener interfaces for actions to execute after tasks have
been completed.
+ Should have no logical/behavioral changes.

Hopefully, this creates a more opaque interface for activities or
other classes to perform these actions as well.

Bug: 21170557
Change-Id: I43aea7e37600d3978e285f047cba7ce75ebb5787