BUG/MINOR: cli: Fix memory leak

Valgrind's memcheck reports memory leaks in cli.c, because
the out parameter of memprintf is not properly freed:

  ==31035== 11 bytes in 1 blocks are definitely lost in loss record 16 of 101
  ==31035==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  ==31035==    by 0x4C2FDEF: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  ==31035==    by 0x4A3C72: my_realloc2 (standard.h:1364)
  ==31035==    by 0x4A3C72: memvprintf (standard.c:3459)
  ==31035==    by 0x4A3D93: memprintf (standard.c:3482)
  ==31035==    by 0x4AF77E: mworker_cli_sockpair_new (cli.c:2324)
  ==31035==    by 0x48E826: init (haproxy.c:1749)
  ==31035==    by 0x408BBC: main (haproxy.c:2725)
  ==31035==
  ==31035== 11 bytes in 1 blocks are definitely lost in loss record 17 of 101
  ==31035==    at 0x4C2DB8F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  ==31035==    by 0x4C2FDEF: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  ==31035==    by 0x4A3C72: my_realloc2 (standard.h:1364)
  ==31035==    by 0x4A3C72: memvprintf (standard.c:3459)
  ==31035==    by 0x4A3D93: memprintf (standard.c:3482)
  ==31035==    by 0x4AF071: mworker_cli_proxy_create (cli.c:2172)
  ==31035==    by 0x48EC89: init (haproxy.c:1760)
  ==31035==    by 0x408BBC: main (haproxy.c:2725)

These leaks were introduced in commits
ce83b4a5dd48c000dec68f9d551945d21e9ac7ac and
8a02257d88276e2f2f10c407d2961995f74a192c
which are specific to haproxy 1.9 dev.
diff --git a/src/cli.c b/src/cli.c
index 0ec8dc8..b89bc21 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -2207,8 +2207,12 @@
 		newsrv->conf.line = 0;
 
 		memprintf(&msg, "sockpair@%d", child->ipc_fd[0]);
-		if ((sk = str2sa_range(msg, &port, &port1, &port2, &errmsg, NULL, NULL, 0)) == 0)
+		if ((sk = str2sa_range(msg, &port, &port1, &port2, &errmsg, NULL, NULL, 0)) == 0) {
+			free(msg);
 			return -1;
+		}
+		free(msg);
+		msg = NULL;
 
 		proto = protocol_by_family(sk->ss_family);
 		if (!proto || !proto->connect) {
@@ -2364,9 +2368,12 @@
 	}
 
 	if (!str2listener(path, global.stats_fe, bind_conf, "master-socket", 0, &err)) {
+		free(path);
 		ha_alert("Cannot create a CLI sockpair listener for process #%d\n", proc);
 		return -1;
 	}
+	free(path);
+	path = NULL;
 
 	list_for_each_entry(l, &bind_conf->listeners, by_bind) {
 		l->maxconn = global.stats_fe->maxconn;