unix-manager: fix memleak

This fixes:

2,595 (1,824 direct, 771 indirect) bytes in 57 blocks are definitely lost in loss record 328 of 332
   at 0x4C29C0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x66D0C7B: ??? (in /usr/lib/x86_64-linux-gnu/libjansson.so.4.7.0)
   by 0x911A27: UnixManagerListCommand (unix-manager.c:766)
   by 0x9108A9: UnixCommandExecute (unix-manager.c:486)
   by 0x910D9E: UnixCommandRun (unix-manager.c:545)
   by 0x9111B3: UnixMain (unix-manager.c:593)
   by 0x913D27: UnixManager (unix-manager.c:961)
   by 0x907773: TmThreadsManagement (tm-threads.c:600)
   by 0x68DE283: start_thread (pthread_create.c:333)
   by 0x80A6A4C: clone (in /lib/x86_64-linux-gnu/libc-2.21.so)

src/unix-manager.c

@@ -763,7 +763,7 @@ TmEcode UnixManagerListCommand(json_t *cmd,
     }
 
     TAILQ_FOREACH(lcmd, &gcmd->commands, next) {
-        json_array_append(jarray, json_string(lcmd->name));
+        json_array_append_new(jarray, json_string(lcmd->name));
         i++;
     }