mgr: added yb_first_human_restart (resolves #713)

When bots are playing on dedicated server and first human joins a team the game will be restarted if yb_first_human_restart is higher than zero.

Co-Authored-By: Max <161382234+dyspose@users.noreply.github.com>

src/engine.cpp

@@ -1112,6 +1112,9 @@ void Game::slowFrame () {
       // ensure the server admin is confident about features he's using
       ensureHealthyGameEnvironment ();
 
+      // maintain round restart for first human join
+      bots.maintainRoundRestart ();
+
       // update next update time
       m_halfSecondFrame = nextUpdate * 0.25f + time ();
    }