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 am: 1a1bb632e7
am: d8192c9149

Change-Id: I25ed67aa5671f7484dc99d3d79e0ed33125117f6