unix-manager: fix memleak in error case (CID 1353491)

src/unix-manager.c

@@ -396,6 +396,8 @@ int UnixCommandAccept(UnixCommand *this)
     uclient = UnixClientAlloc();
     if (unlikely(uclient == NULL)) {
         SCLogError(SC_ERR_MEM_ALLOC, "Can't allocate new client");
+        json_decref(server_msg);
+        close(client);
         return 0;
     }
     uclient->fd = client;