Fix wrong grep regular expression for tap ports

The regular expression used in neutron_ovs_base_cleanup omit
prefix in ovs tap ports, so wrong names are returned and used.
E.g. tap devices created for ironic in devstack are brbm-tap1
and ovs-tap1.

Change-Id: I034be6362b3d09c5296ecc413828a056712c3bd2
diff --git a/lib/neutron_plugins/ovs_base b/lib/neutron_plugins/ovs_base
index cde5298..2997c6c 100644
--- a/lib/neutron_plugins/ovs_base
+++ b/lib/neutron_plugins/ovs_base
@@ -28,7 +28,7 @@
 
 function neutron_ovs_base_cleanup {
     # remove all OVS ports that look like Neutron created ports
-    for port in $(sudo ovs-vsctl list port | grep -o -e tap[0-9a-f\-]* -e q[rg]-[0-9a-f\-]*); do
+    for port in $(sudo ovs-vsctl list port | grep -o -e [a-zA-Z\-]*tap[0-9a-f\-]* -e q[rg]-[0-9a-f\-]*); do
         sudo ovs-vsctl del-port ${port}
     done