Refactor: improved working with promises in zabbixAPICore.service.
Refactor: improved working with promises in zabbixAPICore.service.

alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix,alexanderzobnin/grafana-zabbix