[bitnami/mongodb] fix: initial primary host variable for arbiter and hidden replicas

[romanj85]

Description of the change

The environment variable MONGODB_INITIAL_PRIMARY_HOST was incorrectly populated in the original code with the name of its headless service. I.e. for arbiters -> %s-arbiter-headless and for hidden replicas -> "%s-hidden-headless.
The correct arbiter and hidden replicas should always be connected to the headless service running the primary replica - %s-headless - mongodb.service.nameOverride.

Benefits

Arbiter and hidden replicas can join the MongoDB cluster automatically by the first install.

Applicable issues

• fixes arbiter not getting added to replicaset and and arbiter pod restart at first #29393
• The environment variable MONGODB_INITIAL_PRIMARY_HOST contains a headless service name for arbiter and hidden statefulsets different than the one for MongoDB replicas.

Checklist

• Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
• Title of the pull request follows this pattern [bitnami/<name_of_the_chart>] Descriptive title
• All commits signed off and in agreement of Developer Certificate of Origin (DCO)

[romanj85]

This is related to the issue: #29393

[santimar]

Any update on this?
At the moment the mongo cluster created by default chart will stop work if the primary or the secondary go down.
It's supposed to stay up instead