res_xmpp: Correctly check return value of SSL_connect

SSL_connect returns non-zero for both success and some error conditions
so simply negating is inadequate.

Change-Id: Ifbf882896e598703b6c615407fa456d3199f95b1

res/res_xmpp.c

@@ -2664,7 +2664,7 @@ static int xmpp_client_requested_tls(struct ast_xmpp_client *client, struct ast_
 		goto failure;
 	}
 
-	if (!SSL_connect(client->ssl_session)) {
+	if (SSL_connect(client->ssl_session) <= 0) {
 		goto failure;
 	}