tests: skip netlink based tests when resources are not available

* tests/netlink_inet_diag.c (main): Return 77 if socket, bind,
or listen syscall fail.
* tests/netlink_unix_diag.c (main): Likewise.
diff --git a/tests/netlink_inet_diag.c b/tests/netlink_inet_diag.c
index 7d41b0b..bacb938 100644
--- a/tests/netlink_inet_diag.c
+++ b/tests/netlink_inet_diag.c
@@ -81,11 +81,10 @@
 	close(0);
 	close(1);
 
-	assert(socket(PF_INET, SOCK_STREAM, 0) == 0);
-	assert(bind(0, (struct sockaddr *) &addr, len) == 0);
-	assert(listen(0, 5) == 0);
-
-	if (socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG) != 1)
+	if (socket(PF_INET, SOCK_STREAM, 0) ||
+	    bind(0, (struct sockaddr *) &addr, len) ||
+	    listen(0, 5) ||
+	    socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG) != 1)
 		return 77;
 
 	return (send_query(1, AF_INET, IPPROTO_TCP) &&
diff --git a/tests/netlink_unix_diag.c b/tests/netlink_unix_diag.c
index 979ab88..817bf01 100644
--- a/tests/netlink_unix_diag.c
+++ b/tests/netlink_unix_diag.c
@@ -90,9 +90,11 @@
 	close(1);
 
 	(void) unlink(SUN_PATH);
-	assert(socket(PF_LOCAL, SOCK_STREAM, 0) == 0);
-	assert(bind(0, (struct sockaddr *) &addr, len) == 0);
-	assert(listen(0, 5) == 0);
+	if (socket(PF_LOCAL, SOCK_STREAM, 0) ||
+	    bind(0, (struct sockaddr *) &addr, len) ||
+	    listen(0, 5))
+		return 77;
+
 	assert(unlink(SUN_PATH) == 0);
 
 	if (socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG) != 1)