convert from connection_type to compute_driver

connection_type is deprecated for Folsom, now using compute_driver
to specify virt driver. This makes the change so that devstack
uses the prefered way.

Change-Id: I35c5ce64dc329121a61b888d44c05e3c70c6aecc
diff --git a/stack.sh b/stack.sh
index 87865dc..f12eca9 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1803,7 +1803,7 @@
 
 if [ "$VIRT_DRIVER" = 'xenserver' ]; then
     read_password XENAPI_PASSWORD "ENTER A PASSWORD TO USE FOR XEN."
-    add_nova_opt "connection_type=xenapi"
+    add_nova_opt "compute_driver=xenapi.XenAPIDriver"
     XENAPI_CONNECTION_URL=${XENAPI_CONNECTION_URL:-"http://169.254.0.1"}
     XENAPI_USER=${XENAPI_USER:-"root"}
     add_nova_opt "xenapi_connection_url=$XENAPI_CONNECTION_URL"
@@ -1814,7 +1814,7 @@
     XEN_FIREWALL_DRIVER=${XEN_FIREWALL_DRIVER:-"nova.virt.firewall.IptablesFirewallDriver"}
     add_nova_opt "firewall_driver=$XEN_FIREWALL_DRIVER"
 else
-    add_nova_opt "connection_type=libvirt"
+    add_nova_opt "compute_driver=libvirt.LibvirtDriver"
     LIBVIRT_FIREWALL_DRIVER=${LIBVIRT_FIREWALL_DRIVER:-"nova.virt.libvirt.firewall.IptablesFirewallDriver"}
     add_nova_opt "firewall_driver=$LIBVIRT_FIREWALL_DRIVER"
 fi