Don't draw onto a hw surface using the software renderer

Bug #6485955

If an invalidate gets scheduled right before the EGL surface is destroyed,
the next draw pass is done in software. This causes the software renderer
to connect to the surface forever which prevents the hardware renderer
from coming back when the screen is turned back on.

The fix here is to ignore the draw request when hw acceleration is requested
but not yet available. Proper software fallback will still happen when an
error is encountered with hardware rendering (in which case hw acceleration
will not be marked as requested anymore.)

Change-Id: I1edc4a51c8dd38240aa2345092a18a081a756fc1