UpdateMembershipRecord creates supurfluos activity record for every member on every run.
This is because every membership record is updated via crm_update_contact_membership. AFICS this only needs to be done if the calculated status differs from what's stored in the DB. This patch adds checking for this. This also might take care of
CRM-1696 and CRM-2454.
Also removed double logging when a reminder email is sent.
[ * issue submitted by 'Dave Hansen-Lange' * ]