Improve `bin/storage upgrade` behavior when run out-of-order

Summary:
Fixes T5770. This error occurs if you run `bin/storage upgrade` before you set up MySQL credentials.

This isn't what the setup guide says to do, but it's an easy mistake to make and should be a permitted install path since there's no reason you can't do things in this order.

Specifically, we use a mixture of "standard" (configured) and "administrative" (`--user` and `--password`) credentials, and if the standard ones are bogus bad things happen. We use the standard credentials to make some initialization order stuff easier, and because there's no `--host` flag and adding one would be silly, and because we only need administrative credentials to issue ALTER / CREATE statements.

Test Plan: Ran with bad standard credentials; ran with bad administrative credentials. Ran with good credentials.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5770

Differential Revision: https://secure.phabricator.com/D10199