MINOR: tools: make str2sa_range() optionally return the fd

If a file descriptor was passed, we can optionally return it. This will
be useful for listening sockets which are both a pre-bound FD and a ready
socket.
diff --git a/src/check.c b/src/check.c
index 21978da..40788ae 100644
--- a/src/check.c
+++ b/src/check.c
@@ -2638,7 +2638,7 @@
 		goto error;
 	}
 
-	sk = str2sa_range(args[*cur_arg+1], NULL, &port1, &port2, errmsg, NULL, NULL,
+	sk = str2sa_range(args[*cur_arg+1], NULL, &port1, &port2, NULL, errmsg, NULL, NULL,
 	                  PA_O_RESOLVE | PA_O_PORT_OK | PA_O_STREAM);
 	if (!sk) {
 		memprintf(errmsg, "'%s' : %s", args[*cur_arg], *errmsg);