Also applied the following fixes:
===
1. cleaned up some pylint failures that were not spotted before:
Module neutron.objects.qos.policy: Metaclass class method __new__ should
have 'mcs' as first argument
Module neutron.objects.qos.rule: Lambda may not be necessary
===
2. Revert "Introduce the AFTER_READ callback for ports and networks"
This reverts commit e3dba14241.
We don't use callbacks to extend resources anymore, instead relying on
ml2 extension drivers. No need for the patch to achieve QoS, and it also
breaks test_delete_subnet_with_callback that was added in master
recently.
===
3. updated requirements.txt and test-requirements.txt based on:
https://review.openstack.org/#/c/204398/
to avoid requirements gate checks failing due to incompatible
requirements comparing to global-requirements.txt
Change-Id: I744ab2d8327a428a5467f2d07d073a5f8c333520
d3708de0cb