Replace usages of littlemock with mockito

Littlemock appears to have been created as an alternative to
Mockito that would work on Android. Given that Mockito does
now work on Android and Littlemock has had no activity since
Aug 2012 it seems prudent to switch over to use Mockito instead.

https://code.google.com/archive/p/littlemock/

This is being done as part of the work to upgrade Mockito.

Bug: 32912773
Test: Build and install affected APKs, test using am instrument
Change-Id: Id0e57880ea66c5681b664bbfb534c96410544665