MediaPlayerService: fix access of mPlayer in client am: 502c2f4053 am: bd7db202c6 am: 03fa67202f am: 263d5a2a70 am: 0844e1a3e8 am: e0f4963584 am: 5cc9f8780c am: 93ae13644b
am: 50280c1b44

Change-Id: Ie10440f1e789a5b8853726cd91d7705228c3b19f