fix: networkmanager cannot be started within OnClientStopped or OnServerStopped callbacks#3908

NoelStephensUnity wants to merge 2 commits intodevelop-2.0.0Unity-Technologies/com.unity.netcode.gameobjects:develop-2.0.0from

fix/networkmanager-start-from-onstoppedUnity-Technologies/com.unity.netcode.gameobjects:fix/networkmanager-start-from-onstoppedCopy head branch name to clipboard