Only log zone not found when notifing
Only log zone not found when notifing

We are currently logging zone not found when
quering the SOA record. This should only
happen when notifing.

Change-Id: Iad790593a809a165718d3700cf7325f52208dab1
Closes-Bug: #1671636

openstack/designate,openstack/designate,openstack/designate