Do not handle VSync event during resolution switch

When there is a resolution switch, SurfaceFlinger will handle as display
changes. If the VSync comes before the display is ready, the access to
the display will bring exception.

Solution: Add mutex lock between onComposerHalVsync() and
setActiveModeInternal().

Bug: 210378166
Test: run cts-on-gsi -m CtsDisplayTestCases
Change-Id: Ide53b0e5cff3b569593a2ed388d0ea66e0002e9d