cwfs: make /srv/cwfs.cmd redable to receive command output

cwfs: make /srv/cwfs.cmd redable to receive command output

before, cwfs would print everything to /dev/cons. this change
will redirect the output of commands to the /srv/cwfs.cmd pipe
so one can use:

con -C /srv/cwfs.cmd

and not have the fish for the output in /dev/kmesg.

use standard error (/dev/cons) for unsolicited messages as
there is not always a reader on the command file.