Stagefright: idle OMX after ANW errors

This change fixes an issue in Stagefright where the state of an OMXCodec
object can get out of sync with the state of the OMX component.  In
particular, if one of the ANativeWindow functions failed and put the
OMXCodec into the ERROR state, this would cause Stagefright to skip
doing the Executing -> Idle transition.  Without this transition the
freeBuffersOnPort call would never be made, and the MediaBuffers would
end up being leaked (which would also leak the Gralloc buffers they
reference).

Bug: 5333695
Change-Id: I85ea0cf92d18e7ef6d35c7d1e2a7b4e2c9745d34