Listen to external connections on dbserver-mysql role

Summary:
There are 2 kinds of servers where MariaDB is deployed with dbserver-mysql role:

• devserver, where it makes sens to listen to 127.0.0.1
• pure dbserver-mysql clusters, where it needs to accept other machines

This change configures the listen address accordingly.

It's no-op for Docker MySQL and MariaDB containers.

Ref T1803

Test Plan: Deploy on db-B-001, then mysql -H db-B-001

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1803

Differential Revision: https://devcentral.nasqueron.org/D2986