Fix upgrade to zabbix7

[crowleym]

What this PR does / why we need it:

Zabbix 7 has changed behaviour. DB upgrade can only happen if server node is single and not HA configured. DB upgrade is automatically performed by the server node. See comments in #42

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #42

Special notes for your reviewer:

I have disabled the creation of the job that runs the db-inint-script as I do not believe is necessary anymore with new Zabbix behaviour. This is a fundemental change, so rather than delete the template I have just forced the generation condition to false so it is not executed.

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [x] DCO signed
• [x] Chart Version bumped