Issue when creating hostgroup

[bradbeam]

When creating a host group using the api.HostGroupsCreate function I get

Error: -32602 (Invalid params.): Cannot set "internal" for host group "my.hosts.all".

I think the offending line is https://github.com/AlekSi/zabbix/blob/master/host_group.go#L20 where it needs to be marked as omitempty since it sounds like this might be a readonly field [1](but was erroneously noted otherwise if I'm reading the bug details correctly). If I call the api directly Api.Call("hostgroup.create", zabbix.Params{"name": hostgroup}) it works fine.

Using berngp/docker-zabbix container for testing if that helps ( zabbix ui shows 2.4.6 ).

[1]
https://support.zabbix.com/browse/ZBX-9017

[AlekSi]

Thanks!