PVS V595: Pointer was utilized before it was verified against nullptr.

Change-Id: Iba8b7e6160dc237f45080fa7c101fa72e4d8c753
Reviewed-on: https://review.haiku-os.org/c/1643
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

bin/media_client: return 0 on success

In MediaPlay.cpp, media_play returns non-zero value on failure but forgets to return zero on success.

Coverity CID: 1422617

Signed-off-by: Augustin Cavalier <waddlesplash@gmail.com>

Move media_client to bin