Dialer: Can't pop up "Select Path" after export contacts to storage.

Dialer's DialtactsActivity did not receive the result that
the MultiPickContactActivity sent when export contacts.
Add the activity result handler to direct to export path dialog.

CRs-Fixed: 775402

Change-Id: Icf3c3f594984f1ed1c93f7899aa5708d1196dc77