CMFileManager : Dismiss shortcutActivity before proceeding

Issue reproduction steps :

Create shortcut to a file
Launch it
Press back

The shortcut activity never gets dismissed under certain conditions,
this takes care of those.

Change-Id: Ieca832fbb9f70ec54e1dbe22e9b1eac83f633baf
Merge remote-tracking branch 'upstream/cm-10.2' into cm-10.2