Configure pg_HBA for dovecot user

Summary:
This is a follow up for 8919c2cb98b1.

Ref T1931

Test Plan: salt db-A-001 state.sls roles/dbserver-pgsql/server/config

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1931

Differential Revision: https://devcentral.nasqueron.org/D3375