Zabbix

........S. [ZBX-19236] fixed task manager constantly busy with close_problem task if trigger no longer exists but event still exist

Merge in ZBX/zabbix from feature/ZBX-19236-5.0 to release/5.0

* commit 'ecfee7a739b216c45c0313884747176e3142317b':
  ........S. [ZBX-19236] small code style fix
  ........S. [ZBX-19236] small code style fix
  ........S. [ZBX-19236] added locks, made task closing more efficient
  ........S. [ZBX-19236] fixed task closing
  ........S. [ZBX-19236] fixed task manager constantly busy with close_problem task if trigger no longer exists but event still exist