Comment 8 for bug 1455321

To recreate the issue (Create a subnet with allocation pool and create port with fixed_ip by specifying both ip and subnet_id):

neutron net-create vn22
# Create subnet with allocation pool
neutron subnet-create vn22 --allocation-pool start=1.2.3.34,end=1.2.3.36 1.2.3.0/24
# Requested ip is outside the allocation pool
neutron port-create vn22 --fixed-ip subnet_id=c0644fe6-eb22-4620-a58c-fb99ccafb528,ip_address=1.2.3.44

Port create returns error and from then on port-list will fail and also instance ip delete would thrown exception.

This bug is duplicate of https://bugs.launchpad.net/juniperopenstack/+bug/1451701.
Commit needs to be back ported to R2.20.

Additionally, code will be added to avoid exception in case instance_ip_address field is missing in cassandra.

Fix mentioned in comment #7 doesn't fix the issue.