Zabbix

A.F....... [ZBX-8510] fixed possible deadlocks when updating IT services

Before the fix:
- When changing the structure of the IT service graph or updating and deleting related triggers deadlocks could occur. This happened because the IT services have been updated in an undefined order.

After the fix:
- Now when recalculating IT service status, the whole service tree is loaded into memory and then recalculated. After that their statuses are updated ordered by service ID.