Fix surface tracing thread sync issues

Tracing thread was incorrectly reading the drawing state while it was being
updated by the surface flinger main thread. Move the notify to after
composition.

Fixes: 134752356
Test: capture surface flinger trace
Change-Id: I2d77334f616cb4c34e6a57c84ca97425f7983152
Merged-In: I32a59475ced80d7eaa062181c732ce0f9a81cca5