Zabbix

.......... [DEV-2135] fixed proxy unreachable period and unavailable delay

Merge in ZBX/zabbix from feature/DEV-2135-6.5-su7 to master

* commit '118eb2bcc4e2d2389735c55aefe81d2bd98057d8':
  .......... [DEV-2135] fixed sub-issue 6 - proxy unreachable period and unavailable delay