netdev-dpdk: Reset queue number for vhost devices on vm shutdown.

netdev-dpdk: Reset queue number for vhost devices on vm shutdown.

Rather than poll all disabled queues and waste some memory for vms that
have been shutdown, we can reconfigure when receiving a destroy
connection notification from the vhost library.

$ while true; do
  ovs-appctl dpif-netdev/pmd-rxq-show |awk '
  /port: / {
    tot++;
    if ($5 == "(enabled)") {
      en++;
    }
  }
  END {
    print "total: " tot ", enabled: " en
  }'
  sleep 1
done

total: 66, enabled: 66
total: 6, enabled: 2

This change requires a fix in the DPDK vhost library, so bump the minimal
required version to 18.11.2.

Co-authored-by: Ilya Maximets <i.maximets@samsung.com>
Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
Signed-off-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Ian Stokes <ian.stokes@intel.com>