unix: fix TestSCMCredentials after CL 272226

After CL 42765 (*net.UnixConn).ReadMsgUnix returns flags with
MSG_CMSG_CLOEXEC set. Adjust TestSCMCredentials accordingly.

Change-Id: Id7da35bbd94c51433f5f27a0e04827795826c02e
Reviewed-on: https://go-review.googlesource.com/c/sys/+/311390
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/unix/creds_test.go b/unix/creds_test.go
index a192845..483bfb1 100644
--- a/unix/creds_test.go
+++ b/unix/creds_test.go
@@ -89,8 +89,8 @@
 		if err != nil {
 			t.Fatalf("ReadMsgUnix: %v", err)
 		}
-		if flags != 0 {
-			t.Fatalf("ReadMsgUnix flags = 0x%x, want 0", flags)
+		if flags != 0 && flags != unix.MSG_CMSG_CLOEXEC {
+			t.Fatalf("ReadMsgUnix flags = %#x, want 0 or %#x (MSG_CMSG_CLOEXEC)", flags, unix.MSG_CMSG_CLOEXEC)
 		}
 		if n != tt.dataLen {
 			t.Fatalf("ReadMsgUnix n = %d, want %d", n, tt.dataLen)