Define vhost_socket_dir in neutron section

vhost_socket_dir is needed in neutron and linux formulas.
This patch defines a global parameter for it and then references it
in linux and neutron pillars.

Related-PROD: PROD-14413

Change-Id: If54879717857bf71b6c038b9316244a14a9b0668
diff --git a/neutron/compute/nfv/dpdk.yml b/neutron/compute/nfv/dpdk.yml
index c8872c7..0901bb8 100644
--- a/neutron/compute/nfv/dpdk.yml
+++ b/neutron/compute/nfv/dpdk.yml
@@ -1,4 +1,6 @@
 parameters:
+  _param:
+    compute_ovs_vhost_socket_dir: "/run/openvswitch-vhost"
   linux:
     network:
       bridge: openvswitch
@@ -12,7 +14,8 @@
         memory_channels: "${_param:compute_ovs_memory_channels}"
         vhost_socket_dir:
           name: "openvswitch-vhost"
-          path: "/run/openvswitch-vhost"
+          path: "${_param:compute_ovs_vhost_socket_dir}"
   neutron:
     compute:
       dpdk: True
+      vhost_socket_dir: "${_param:compute_ovs_vhost_socket_dir}"