Restart Postgres service if not listening on TCP

What does this MR do?

When switching Postgres from sockets to TCP, it is necessary to restart the PostgreSQL service before GitLab can connect to it. If this isn't done, the reconfigure will likely fail as a result.

This is also documented in our Omnibus instructions for switching PostgreSQL to TCP https://docs.gitlab.com/omnibus/settings/database.html#apply-and-restart-services

Adding this caveat in the Chart docs as well. I thought it was best to copy the relevant content into the Chart docs, but let me know if a link would be preferable and I can go back and fix it up.

Related issues

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