OF-1063: Prevent TimerThread from exiting
OF-1063: Prevent TimerThread from exiting

Do not allow TimerThread to exit when the server becomes heavily loaded,
preferring instead to use the caller's thread to execute a scheduled
task when needed. This may result in a temporary slowdown, but is better
than a hard failure which requires a restart of the server.

Gugli/Openfire,guusdk/Openfire,akrherz/Openfire,igniterealtime/Openfire,igniterealtime/Openfire,speedy01/Openfire,guusdk/Openfire,igniterealtime/Openfire,guusdk/Openfire,Gugli/Openfire,GregDThomas/Openfire,akrherz/Openfire,Gugli/Openfire,speedy01/Openfire,igniterealtime/Openfire,guusdk/Openfire,akrherz/Openfire,speedy01/Openfire,igniterealtime/Openfire,GregDThomas/Openfire,Gugli/Openfire,guusdk/Openfire,GregDThomas/Openfire,speedy01/Openfire,GregDThomas/Openfire,GregDThomas/Openfire,Gugli/Openfire,akrherz/Openfire,akrherz/Openfire,speedy01/Openfire