Remove dependent module py3kcompat

Module py3kcompat was removed from oslo-incubator, we can use
six directly.

Syncing module network_utils:
162e850 Remove import workaround of SplitResult
897aa7c urlsplit issues with IPv6 addresses in python26
35dc1d7 py3kcompat: remove

Change-Id: I71446362209c306c7e8858f4713a59b84fbcc1b2
Closes-Bug: #1280033
Merge "Remove dependent module py3kcompat"