When $wsys doesn't exist (eg, drawterm -G, or
rcpu from a text console), the profile would
create an empty $wsys variable, and sessions
started in this environment would fail with a
null list in concatenation.
This change tests if /mnt/term/env/wsys exists
before assigning it.
on systems with serial console and graphics such as the raspberry pi,
it is nice to get a system shell on the serial console even when no
monitor is connected.
this makes sure tcp boot will have ther user /tmp's
the same way as from local cwfs. we used /srv/cwfs
to prevent a deadlock with 9660srv as a root filesystem
which has been fixed now.