stagefright: Cancel audioCheck event when setting nativewindow

In html5 playback, setNativeWindow_l() will be called twice
when switching from landscape to portrait mode. If the 2nd
setNativeWindow_l gets the LOCK before proceeding mCheckAudioStatusEvent
posted in the 1st setNativeWindow_l, it will get the infomation
that seeking is completed and won't do seeking in this run.

CRs-fixed: 624469
Change-Id: Ia5c4e373e8a71b907b15b913085600d9481ef982
libstagefright/omx: Fix CallbackDispatcher dereference in callback.

    - findDispatcher can return NULL. Check for NULL.

Change-Id: I07edc427b706dfdeec6a6f90f13d00c8941e77f2
RTSP: Fix crash issue while repeated pause/resume

While doing repeated pause-resume operation in RTSP streaming,
some times, the accessunit timeout check is being posted when
the streaming paused, and even after receving the EOS.
Due to this check, after the EOS, the number of packets received
will be zero and the session gets Teardown while the
streaming is paused. Upon resume, it leads to check failure and crash.

Changes are done such that the accessunit timeout check will
not be done in pause/seek state.

CRs-Fixed: 636312

Change-Id: I60d09d5394eed59a8e2bbf5556628f1ea26f7807