Specify a separate dir for vhost_user sockets

Currently when OVS-DPDK is enabled, instances fail to spawn
due to permissions mismatch, see nova bug for details:
https://bugs.launchpad.net/nova/+bug/1670950

This patch configures OVS to use a separate dir, created by
nova formula [1].

[1] https://gerrit.mcp.mirantis.net/11213

Related-PROD: PROD-14413

Change-Id: Ia86658b0967b4d35f063c7f6f53e26e78a1fbd39

linux/network/dpdk.sls

 ]
 %}
 
+{%- if network.openvswitch.get('vhost_socket_dir',{}).get('path') %}
+{%- do ovs_options.append("vhost-sock-dir=\""+network.openvswitch.vhost_socket_dir.path+"\"") %}
+{%- endif %}
+
 {%- for option in ovs_options %}
 
 linux_network_dpdk_ovs_option_{{ option }}:

tests/pillar/network_openvswitch_dpdk.sls

       dpdk_socket_mem: "1024"
       dpdk_lcore_mask: "0x400"
       memory_channels: "2"
+      vhost_socket_dir:
+        name: "openvswitch-vhost"
+        path: "/run/openvswitch-vhost"
     interface:
       dpdk0:
         name: enp5s0f1