files: Add case::default in open_fd

Otherwise I'm getting error
 |
 | files.c: In function ‘prepare_fds’:
 | files.c:329:23: error: ‘tmp’ may be used uninitialized in this function [-Werror=uninitialized]
 | files.c:309:6: note: ‘tmp’ was declared here
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files.c

@@ -318,6 +318,9 @@ static int open_fd(int pid, struct fdinfo_entry *fe,
 	case FDINFO_INETSK:
 		tmp = open_inet_sk(fe);
 		break;
+	default:
+		tmp = -1;
+		break;
 	}
 
 	if (tmp < 0)