MountService: Fix android.process.media crash repeatedly problem

When the framework restarts because of certain exception, the
external volume id will disappear. At this time, mount service
will issue "volume list" command to vold to get the status of
each storage.

The fix is to re-broadcast the uuid and user label again via
vold "volume list broadcast" command.

Bug: 16253597
Bug: 16306775
Change-Id: I227e8bc597a4f5338035d3401036490f14557211