Merge LibvirtBridgeDriver class into LibvirtGenericVIFDriver

This introduces the LibvirtGenericVIFDriver class which uses
the 'vif_type' mapping field to determine what type of host
network configuration is required.

The LibvirtBridgeDriver class functionality is merged into
LibvirtGenericVIFDriver. For backwards compatibility with
the Folsom release, the existing LibvirtBridgeDriver class
is made to inherit from LibvirtGenericVIFDriver and directly
call the bridge specific setup APIs. This eases migration to
the new VIF impl during the Grizzly deployment lifecycle, with
an expectation that the LibvirtBridgeDriver stub will be
deleted in the Hxxxxx release.

DocImpact
Blueprint: libvirt-vif-driver
Change-Id: I948158b5ee0a97f666bb4d21020b552d3475b6d3
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
iptables-restore error when table not loaded.

When adding openstack rules, if a table module is not loaded,
the resulted file doesn't include the section for the missing
table, making new rules added to it, out of place and
a no valid file for iptables-restore

Fixes bug #1103436

Change-Id: I34ae51a23efec57bfec37b8fa378d043fcf62d70
Make sure there are no unused import

Remove all currently unused imports
Prevent future unused imports

Change-Id: I6ac26d5c71b79952a7732db300355a00310c712e
Merge "Make sure there are no unused import"
Merge "iptables-restore error when table not loaded."
Merge "Merge LibvirtBridgeDriver class into LibvirtGenericVIFDriver"