Allow tempest to dump the ovs db

Looks like in several cases the port used by VMs are trunk port
instead of access port, would be nice if we could make those kind of
issues more visible on the gate runs.

Change-Id: I2eef98188446a4e8bee8a0c9f7f3a7366797a948

functions.sh

@@ -345,6 +345,7 @@ function setup_host {
     TEMPFILE=`mktemp`
     echo "tempest ALL=(root) NOPASSWD:/sbin/ip" >$TEMPFILE
     echo "tempest ALL=(root) NOPASSWD:/sbin/iptables" >>$TEMPFILE
+    echo "tempest ALL=(root) NOPASSWD:/usr/bin/ovsdb-client" >>$TEMPFILE
     chmod 0440 $TEMPFILE
     sudo chown root:root $TEMPFILE
     sudo mv $TEMPFILE /etc/sudoers.d/51_tempest_sh