Use single db_host when multi postgresql::listen_adresses
Fixes #1166 (closed)
Postgresql allows to listen on multiple adresses: https://www.postgresql.org/docs/9.5/static/runtime-config-connection.html#listen_addresses
ActiveRecord accept one host for a connection (seems legit)
This commit allow user to specify in ['gitlab']['postgresql']['listen_address']
and ['gitlab-ci']['postgresql']['listen_address']
multiple addresses, comma-separated, as accepted by Postgresql.
In parsing time, it take as db_host
the first ip from the list.
cc @marin