Fix Q_USE_PUBLIC_VETH regression

A recently merged change Ie35cb537bb670c4773598b8db29877fb8a12ff50
and I71e2594288bae1a71dc2c8c3fb350b913dbd5e2c broke Q_USE_PUBLIC_VETH.
This commit fixes the regression.

Closes-Bug: #1436637
Change-Id: I1447bf98607143ba4954ce5ec3ed94010320baa5
diff --git a/lib/neutron-legacy b/lib/neutron-legacy
index e9a3926..d3dd8dd 100755
--- a/lib/neutron-legacy
+++ b/lib/neutron-legacy
@@ -1263,7 +1263,7 @@
         if is_neutron_ovs_base_plugin && [[ "$Q_USE_NAMESPACE" = "True" ]]; then
             local ext_gw_interface=$(_neutron_get_ext_gw_interface)
             local cidr_len=${FLOATING_RANGE#*/}
-            if [[ $(ip addr show dev $ext_gw_interface | grep -c $ext_gw_ip) == 0 && $Q_USE_PROVIDERNET_FOR_PUBLIC == "False" ]]; then
+            if [[ $(ip addr show dev $ext_gw_interface | grep -c $ext_gw_ip) == 0 && ( $Q_USE_PROVIDERNET_FOR_PUBLIC == "False" || $Q_USE_PUBLIC_VETH == "True" ) ]]; then
                 sudo ip addr add $ext_gw_ip/$cidr_len dev $ext_gw_interface
                 sudo ip link set $ext_gw_interface up
             fi