Update quota notify limit alerts users if they are now over threshold

Bug 1367539

When the admin adjusts the quota notify threshold limit the system
alerts any users that are now over limit that haven't been already
alerted on previous limit

Change-Id: I1d99b88336ef3be50dfa3b1453e9e351c701d739
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>