single user mode broken on RELENG_7

[[LoN]Kamikaze]

Since I switched to RELENG_7 I cannot use /rescue/vi in single user mode any
more. It will just print everything in the bottom line of the screen, so it's
impossible to navigate in a document or see what you're doing.

Mounting /usr and starting vim displays everything properly, but none of the
keys work. The screen is just frozen until I hack a couple of :q! into the
keyboard.

It's kinda tedious to fix my misconfigurations with cat and sed. I wish for
the RELENG_6 behaviour to return (that is, being able to use vi).