LibvirtBridgeDriver now LibvirtGenericVIFDriver

fixes bug 1106441

In Grizzly, inheritance is such that LibvirtGenericVIFDriver does
the same job as LibvirtBridgeDriver, and there are long term (H/I)
plans to retire libvirtBridgeDriver. This patch updates the config
reference.

Change-Id: Ie571b86f8559218f0c7a54f273b56a24c4543afd
Compute Admin Chapter 1 Anti-Cruft

This patch contains random fixes to sections from Chapter 1 of the
Compute Admin guide to lean it and make it more relevant to Grizzly.

Change-Id: Ia67f39c05eacf5d985d0bbb2dd3c63a5055b9cf9
Merge "LibvirtBridgeDriver now LibvirtGenericVIFDriver"
Merge "Compute Admin Chapter 1 Anti-Cruft"