SF: Fix warnings in tests and enable -Werror

Fixes unused-parameter warnings in the vsync and waitforvsync tests,
and enables -Werror in their respective Android.mks.

Bug: 36678673
Test: mm -j, observe no compiler warnings/errors
Change-Id: I6e2c5d2d2937b045794a53d90aeab7653b42e6c5