Fixes for alsa device reservation
* Don't attempt to use device reservation when card_to_num() mapping
has failed. In case of card_to_num() failures, "Audio-1" device
was reserved on start but not released on stop. This was causing
next start to fail with out of memory error, and since previous
commit, with "A handler is already registered for
/org/freedesktop/ReserveDevice1/Audio-1" error.
* In case of playback device reservation failure, release the
capture device
* Remove unused fReservedCaptureDevice and fReservedPlaybackDevice
data members of the JackAlsaDriver class