Eliminate redundant changes to hardware vsync state.

When transitioning between NORMAL and DOZE power modes
we were redundantly calling resyncHardwareVsync.

Similarly, when transitioning from DOZE_SUSPEND to OFF
we were redundantly calling disableHardwareVsync.

This change eliminates those redundant calls.

Fixes bug 62235417

Change-Id: I513bbf94a7ab973ab258efe16436441ac2379b70