Allowing better sql when deleting of old notifications when
multirecipientnotification is enabled - as the code is similar to the
way account/activity/index.json.php used to be.

See patch 4144 for the change to account/activity/index.json.php

Change-Id: If7dce9527ec585b1968cbaff9028679ce7b93bcd
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>