Install conntrack in XenServer Dom0

Neutron openvswitch agent running in compute node will control the
actual connection of the VMs in Dom0 via conntrack-tools, but Dom0
doesn't install conntrack-tools RPM by default.
This patch is to add such support with XenServer 7.0 and above.

Change-Id: Iec56db761015d4b7baa5a5f54314f4ff3fa67e02
diff --git a/lib/nova_plugins/hypervisor-xenserver b/lib/nova_plugins/hypervisor-xenserver
index e75226a..e5d25da 100644
--- a/lib/nova_plugins/hypervisor-xenserver
+++ b/lib/nova_plugins/hypervisor-xenserver
@@ -87,6 +87,7 @@
         cat $TOP_DIR/tools/xen/functions
         echo "create_directory_for_images"
         echo "create_directory_for_kernels"
+        echo "install_conntrack_tools"
     } | $ssh_dom0
 
 }