default gateway regex: use exact match for iface name

If the current interface has a default gateway configured is
determined by the regex

  default.+<interface-name>

If for example 'enc1' is used, but also an interface 'enc1800' is
present, the regex will also match the 'enc1800' default gateway.

This patch fixes this by looking for <interface-name><white-space>.
This way 'enc1800' is not matched.

Change-Id: Id1d58f5be6296c3a37aef788359ae8fe0fe11d8b
diff --git a/lib/neutron-legacy b/lib/neutron-legacy
index 1dfd5fe..a409164 100644
--- a/lib/neutron-legacy
+++ b/lib/neutron-legacy
@@ -570,7 +570,7 @@
         local IP_DEL=""
         local IP_UP=""
         local DEFAULT_ROUTE_GW
-        DEFAULT_ROUTE_GW=$(ip -f $af r | awk "/default.+$from_intf/ { print \$3; exit }")
+        DEFAULT_ROUTE_GW=$(ip -f $af r | awk "/default.+$from_intf\s/ { print \$3; exit }")
         local ADD_OVS_PORT=""
         local DEL_OVS_PORT=""
         local ARP_CMD=""