emulator opengl: Fix bug when re-binding the same context

When re-binding the same context the resoult was that the
surfaces got unbinded from the context.
Fixed that situation and added an optimization to do nothing
in case of re-binding the same context to the same binded surfaces.

Change-Id: Ic7058723399b0807d902c29b4170c7465c02bb99
1 file changed