Set integration bridge in localrc

XEN_INTEGRATION_BRIDGE should point to the dom0 bridge that serves the
purpose of the integration bridge. The value will be taken from the
DEVSTACK_GATE_XS_INT_BR parameter. In normal cases this value is
injected through kernel parameters, however we don't have that
information in the cloud based OSCI.
Enable q-domua service

XenServer with an All in One installation uses two agent. q-domua is
managing the "Network node switch", whereas q-agt is managing the
"Compute" switch. This change hacks in the enablement of those services.
Enable user to inject Flat network bridge

As Neutron cannot use XenServer network name-labels to identify
switches, we need to specify the bridge name. The idea is that in an
earlier phase of the test run we export the DEVSTACK_GATE_XENAPI_FLATNET
variable wit the appropriate name, and we use that value here.