[PATCH, go]: Disable TestListenMulticastUDP on alpha linux

[Uros Bizjak]

Hello!

alpha linux does not have expected "/proc/net/igmp" and
"/proc/net/igmp6" files, so "func interfaceMulticastAddrTable(ifindex
int)" from interface_linux.go always returns (nil, nil), failing
net/test with:

--- FAIL: net.TestListenMulticastUDP (4.71 seconds)
        ???:1: IPv4 multicast interface: <nil>
        ???:1: IPv4 multicast TTL: 1
        ???:1: IPv4 multicast loopback: false
        ???:1: "224.0.0.254:12345" not found in RIB
FAIL

Attached patch skips this sub-test in the same way as for ARM arch.

Tested on alphaev6-pc-linux-gnu, where it "fixes" failing net test.

Uros.

Index: go/net/multicast_test.go
===================================================================
--- go/net/multicast_test.go    (revision 184156)
+++ go/net/multicast_test.go    (working copy)
@@ -33,7 +33,7 @@
        case "netbsd", "openbsd", "plan9", "windows":
                return
        case "linux":
-               if runtime.GOARCH == "arm" {
+               if runtime.GOARCH == "arm" || runtime.GOARCH == "alpha" {
                        return
                }
        }