Fix memory leak in netengine.c (#1411)

This is in response to issue #1366
The clang static analyzer basically claims that there is a memory leak
happening in `set_ssl_ctx` for the variable `args`. The leak is
triggered when the base event `base` is NULL and the condition within
`set_ssl_ctx` is not triggered. Therefore as a patch I am adding an else
condition to free it. (It cannot be freed after the event is created by
`event_new` because `args` can be invoked as argument for callback
function later on)

Please let me know if this patch is helpful :)

---------

Co-authored-by: Pavel Punsky <eakraly@users.noreply.github.com>

src/apps/relay/netengine.c

@@ -349,6 +349,10 @@ void set_ssl_ctx(ioa_engine_handle e, turn_params_t *params) {
     args->next = params->tls_ctx_update_ev;
     params->tls_ctx_update_ev = ev;
     TURN_MUTEX_UNLOCK(&turn_params.tls_mutex);
+  } else {
+    if (args) {
+      free(args);
+    }
   }
 }