Don't raise RetryRequest for port in delete_subnet
Don't raise RetryRequest for port in delete_subnet

The loop already takes care of requerying for ports in new
transactions so throwing a RetryRequest is just a waste of
time (due to sleep back-off) and retry limits.

Change-Id: If48586d54d55c89dd254f18f21411ac3d230c87f

cloudbase/neutron,noironetworks/neutron,sebrandon1/neutron,mahak/neutron,sebrandon1/neutron,cloudbase/neutron,mahak/neutron,huntxu/neutron,eayunstack/neutron,huntxu/neutron,eayunstack/neutron,openstack/neutron,openstack/neutron,noironetworks/neutron,mahak/neutron,openstack/neutron