netdev-dpdk: Fix dpdk_watchdog failure to quiesce.
Fix issue whereby vhost_thread is waiting for dpdk_watchdog
thread to quiesce and at the same time dpdk_watchdog thread
is waiting for vhost_thread to give up dpdk_mutex.
Reported-by: Patrik Andersson R <patrik.r.andersson@ericsson.com> Signed-off-by: Patrik Andersson R <patrik.r.andersson@ericsson.com> Signed-off-by: Kevin Traynor <kevin.traynor@intel.com> Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com>