Minor post-merge cleanup.

Change-Id: Ic65ef882b61aa6506d21bbe41b9ac8473a950591
StorageManager: fix android.process.media process stop while plug a discontinuous partitioned SD Card

While get volume state, throw an IllegalArgumentException, catch
this exception in StorageManager and return null to MtpService to
avoid process stoping.

Change-Id: Iebb5c38e375d3f54505d9b9d64fcd0f02a2b60c1
Author: Li Gang <gang.g.li@intel.com>
Signed-off-by: Li Gang <gang.g.li@intel.com>
Signed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 47459