Mattermost blocks on pinging database

[amy.blais]

Hi @VoyagesDivins, as a first step, wondering if some of these earlier threads might help:

• [Solved] Failed to ping db err
• [SOLVED] Trouble during instalation, failed to ping DB
• https://github.com/mattermost/mattermost-server/issues/6860
• https://stackoverflow.com/questions/42039274/mattermost-3-6-2-ubuntu-16-04-pgsql-9-5-db-dial-err-issue