Clean expired passwords causes error when upgrading (bug 1369370)

When upgrading, should only check if the cron job
'auth_clean_expired_password_requests' already exists
in the table - without all the other fields that need to be updated.
Otherwise, it will check on all the fields (i.e. minute, hour, etc).
If the admin updated them,
the check won't match and a duplicate error results.

Change-Id: I2d30ac97e9a82aaf0d538a834396fdc2d2757480
Signed-off-by: Ghada El-Zoghbi <ghada@catalyst-au.net>
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>