Add cluster vm specialties

[JeGoi]

Is your feature request related to a problem? Please describe. Define vm specialties cluster.conf. Based on that specialty, we some services can be disabled, some monit can be check for specific vm. The main id is to enable by default and disable for specific usage: For exemple, some node may never have the DB, then we should be able to disable de db in the cluster.conf.

NOTE in case of DB: Be careful about service dependencies and generate conf for mariadb

Describe the solution you'd like You define a member of the cluster as a DB or Load Balancer and service config or monit check are taking care of that specialties to check or validate running services, members of a group, etc. Exemple: https://github.com/inverse-inc/packetfence-monitoring-scripts/blob/master/scripts/functions.sh#L117 Return the DB members instead of all members.

Describe alternatives you've considered You can use the multi_zone=enabled to define group members for need groups (DB, APP). Then select services to enable or not.

Additional context