Stagefright: Transition to uninitialized state after freeing node

If the component is force-released after timeout, there could be
a race condition where component posted a message just before it
was released. This posted message will cause ACodec to wrongly
invoke OMX API on the component which was freed already.
Move ACodec to uninitialized state where all component messages
will be safely ignored.

Change-Id: I71da7c7d021210fd6bed44761740161a5d8894e7
CRs-Fixed: 884165