remove rc and login.conf files prior to extraction of the new

remove rc and login.conf files prior to extraction of the new
rc and login.conf files from the /etc directory on the floppy.

This prevents the overwrite yes/no prompt from occuring in gzip.
(some PicoBSD disks use gzip and some use minigzip, so the gzip -f flag (force)
is not an option. minigzip has a different meaning for the -f flag.}