DeskClock: Fixed the ringtone name display incorrect when delete music file

It only displays FALLBACKRING when set alarm ringtone by file explorer,
is caused by that it not handle the file uri which from file explorer
in getRingToneTitle method.

Add the judgement to get the file uri and get the right title of alarm
ringtone.

Change-Id: I666db6e29dce58a3c7f0c78beb4fe5643c22f110
CRs-Fixed: 546747