noVNC master no longer stable/folsom compatible

Change-Id: I06ac432ffd6ec82fa1c6a994ebdadc375c0f8f1e
Fixes: bug #1083189
nova-manage network commands only when n-net enabled

This patch checks if n-net is enabled rather than any nova service
before creating networks through nova. Fixes bug 1073313

Change-Id: I8810737ddbb26a5e281060f5395cfad5d186b6d3
Use apt git package instead of git-core.

The git-core package is deprecated in favor of the git package. Use the
git package instead.

Change-Id: Ib136e34c7a0d4f87b02e32996420b3f507ca0bf4