Avoid redundant setMatrix calls from setMatrixInTransaction

This matches the behavior of setPositionInTransaction and setSizeInTransaction.

By eliminating calls to setMatrix, we avoid triggering redundant
SurfaceFlinger invalidates. This is particularly noteworthy on Android
Wear where we must update the minute hand every 60 seconds, but want the
device to spend as much time sleeping as possible.

See b/31489482

Change-Id: I424bb9f60c3033921fa04e7abcfc552500114f1f