Create a single if_root test skipping decorator.
Skip tests if not root.
Lint fixes.
Merge remote-tracking branch 'refs/remotes/origin/master' into iptables-requires-root-839
Address review comment: Remove another root check.
Merge remote-tracking branch 'refs/remotes/origin/master' into iptables-requires-root-839

Conflicts:
	flocker/volume/functional/test_service.py
Merge pull request #854 from ClusterHQ/iptables-requires-root-839

Iptables requires root for tests.

Fixes #839.