Fix isinstance assertions

self.assertIsInstance is preferred over assert(isinstance(..)). See feedback in:
https://review.openstack.org/#/c/102754/1/neutron/tests/unit/test_extension_security_group.py

Change-Id: I9dd6141d8f25961eb42a390b45e6d94d482afc1c
Omit mode keyword when spawning dnsmasq with some ipv6 subnets

Fix UnboundLocalError for certain cases of ipv6 subnets

Closes-Bug: #1335959
Change-Id: I5e4b94d9ba1b13b72e2300b53d5638968e0d3401
Merge "Fix isinstance assertions"
Merge "Omit mode keyword when spawning dnsmasq with some ipv6 subnets"