When external display is connected during video playback, the
flags to overlay was not set properly.
Pass the flags which comes from the hwc, by just changing the
WAIT_FOR_VSYNC(external should not wait for vsync)
(cherry picked from commit 857cfcba2d120d5da4916c7cb4fe119a08d1ce68)
Change-Id: I13100bebd223780eb9c709f384f0e4644e8295dc