fix zabbix-agent service

[tiroso]

What this PR does / why we need it:

In case of zabbix-proxy deployment, the service of zabbix-agent as a sidecar is wrong pointed.

Which issue this PR fixes

• fixes #53

Special notes for your reviewer:

Checklist

• [x] DCO signed
• [x] Chart Version bumped
• [x] n.a. Variables are documented in the README.md

[tiroso]

Bump