Fix for invalid literal ValueError parsing ipv6 url(s)

Switch to using network_utils for splitting the URL. The code
in oslo-incubator supports ipv6 urls

HEAD of oslo-incubator is bb52a3fc49f033b9f36238231ca56e754a78cf4b

Updated openstack-common.conf to pick up the new dependency from
oslo-incubator

Change-Id: Ifa3dec384e85942a191260d17e8141030d31ff84
Closes-Bug: #1298137
Merge "Fix for invalid literal ValueError parsing ipv6 url(s)"