More network debugging detail

* devstack-vm-gate-wrap.sh: Sometimes devstack-gate runs fail for
reasons related to the local network. Include IPv6 addresses in
addition to the IPv4 addressing previously displayed, and add
routing and ARP tables as well.

Change-Id: I771b6081758020cf1521443d1bd15a27ede7f2b1
Add support XenAPI driver

While there will be many more required changes, adding the initial hooks
to support selecting the XenAPI driver when building a localrc file.

Change-Id: I16639141008a07f8241952b9b2f3d3760f9716b9
Add parameters to localrc
Set public interface to eth4
Set default image
Amend network config
Set host ip - so that glance is listening there
Fix comment
Set SERVICE_HOST

As it turned out, that SERVICE_HOST is explicitly specified.
Disable firewall
Only run one test - that I am interested in
Disable agent, use xvdb for volumes
Set multi-host explicitly
Do not run any tests
Put back test execution