The gccgo bug report https://gcc.gnu.org/PR65785 points out that the
multicast listen tests will use the network even with -test.short.
Fix test by checking testing.Short with a nil interface.
Change-Id: I7eab8df34fe3b78fc376912312fac9d0f94977f1
Reviewed-on: https://go-review.googlesource.com/17154
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
                // routing stuff for finding out an appropriate
                // nexthop containing both network and link layer
                // adjacencies.
-               if ifi == nil && !*testExternal {
+               if ifi == nil && (testing.Short() || !*testExternal) {
                        continue
                }
                for _, tt := range ipv4MulticastListenerTests {
                // routing stuff for finding out an appropriate
                // nexthop containing both network and link layer
                // adjacencies.
-               if ifi == nil && (!*testExternal || !*testIPv6) {
+               if ifi == nil && (testing.Short() || !*testExternal || !*testIPv6) {
                        continue
                }
                for _, tt := range ipv6MulticastListenerTests {