xenapi: Cleanup networking

OpenStack VM had 4 interfaces, from which eth0 was connected to HIMN (Host
Internal Management Network), and not used at all. The reason for not
using this interface according to johngarbutt is:
 - VNC console would not work
 - migrations would not work
 - many other things
This change removes the interface, thus devstack is providing the
same architecture as described in the official documentation, YAGNI
applied on the HIMN:

    http://goo.gl/dmrNF

The change also modifies some defaults, so it's easier to get started:
 - The Ubuntu VM is network-installed through the management network
 - OS VM is getting its address on the management network through DHCP
 - Default Public IP addresses aligned to stack.sh defaults
 - OS Services are listening on Management Interface

Related to blueprint xenapi-devstack-cleanup

Change-Id: I73c9751ade6f4786b8b682a1994cb87f0a624379
diff --git a/stack.sh b/stack.sh
index 4089531..9321b42 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1001,6 +1001,9 @@
 
     if [ "$VIRT_DRIVER" = 'xenserver' ]; then
         echo_summary "Using XenServer virtualization driver"
+        if [ -z "$XENAPI_CONNECTION_URL" ]; then
+            die $LINENO "XENAPI_CONNECTION_URL is not specified"
+        fi
         read_password XENAPI_PASSWORD "ENTER A PASSWORD TO USE FOR XEN."
         iniset $NOVA_CONF DEFAULT compute_driver "xenapi.XenAPIDriver"
         iniset $NOVA_CONF DEFAULT xenapi_connection_url "$XENAPI_CONNECTION_URL"