Figure out what to do when someone logs into the regular JustFix.nyc site with a NORENT signup

[toolness]

Currently we send them to LOC, which isn't great.

Introduced by #1230.

[toolness]

Note that for non-NYC users, we let them know that they can't access our services on JustFix.nyc, so that's good at least (we actually had a few situations where non-NYC users were able to send LOCs before we introduced this!).