meta-google: gbmc-bridge: Conditionally advertise default route

We only want to advertise that we have a default route if we have an
external (non-bridge) interface that has a default route. This
disambiguates routes on the internal machine network to avoid
blackholes.

Change-Id: I4059ddf0f74a0b15ca3f93f096b79415a851d3f7
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/meta-google/recipes-google/networking/gbmc-bridge/-bmc-gbmcbr.network.in b/meta-google/recipes-google/networking/gbmc-bridge/-bmc-gbmcbr.network.in
index 09ef620..a2bfc0d 100644
--- a/meta-google/recipes-google/networking/gbmc-bridge/-bmc-gbmcbr.network.in
+++ b/meta-google/recipes-google/networking/gbmc-bridge/-bmc-gbmcbr.network.in
@@ -11,4 +11,4 @@
 [IPv6AcceptRA]
 DHCPv6Client=false
 [IPv6PrefixDelegation]
-RouterLifetimeSec=30
+RouterLifetimeSec=0