Add force_resize_to_same_host option

Instance resize is kind of migration, but not block-migration, so it cannot be
performed without shared storage for instance drives if resized instance is
scheduled to other node (not the node it ran on before resize).

This commit adds option force_resize_to_same_host that forces resized instance
to be scheduled to the node it was running before resize, which fixes
the problem.

Issue: altai-150
Change-Id: Id605b8fa0c3181344cd71c8790e8cbc65785a85d
Make it possible to disable fixed_range-related iptables rules

Now if fixed_range option set to empty string, we don't add any rules
with it to nova POSTROUTING chain.

Issue: altai-90
Change-Id: I986d7ab293cafc7e2ebe6f7cc1d1d1b46f94a265