Remove 'persisted dirty' log message
Remove 'persisted dirty' log message

In a gate run the neutron.quota.resource module logged 5235
lines from this module, making it one of the top offenders.
This single line accounted for 3297 of those entries and it
offers limited information since the quota engine is quite
stable at this point and debugging tenants' dirty status isn't
an issue that comes up.

We can just get rid of this particular log line.

Change-Id: I9cb0fcfbad51a0863d04fb89fbb8b09e3e21bdf0
Partial-Bug: #1707307

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