Fix potentially borked test case

If interface 'lo' is not available, `socket_set_option()` may warn,
which would cause the test to be marked as borked.  Thus we silence the
function call.

Author: cmb69

ext/sockets/tests/mcast_ipv4_recv.phpt

@@ -8,7 +8,7 @@ if (!extension_loaded('sockets')) {
 if (getenv('SKIP_ONLINE_TESTS')) die('skip online test');
 $s = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
 $br = socket_bind($s, '0.0.0.0', 3000);
-$so = socket_set_option($s, IPPROTO_IP, MCAST_JOIN_GROUP, array(
+$so = @socket_set_option($s, IPPROTO_IP, MCAST_JOIN_GROUP, array(
 	"group"	=> '224.0.0.23',
 	"interface" => 'lo',
 ));