As of Oct-25-2018, the NO_EXASCII flag was set in the autoterm variable
when there was no ANSI terminal auto-detected. This defeated the short
inactivity timeout feature of login.js because it was checking specifically
for a zero-value autoterm.

So change this logic to check for no ANSI, PETSCII, or UTF-8 (the 3 indicators
of a valid terminal) - though I suppose PETSCII is questionable (it's not
actually auto-detected, just a non-standard port usually).