DeskClock: Recreate alarms DB on downgrade

This fixed the cm10 to cm10.1 transition (from version 7 to 6)

Change-Id: Ic591ac95af72af7ec5defb2b2a236bb134d414b1
JIRA: CYAN-1188
Issue: https://jira.cyanogenmod.org/browse/CYAN-1188
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>