The regular sshd daemon and the gsi enabled gsisshd daemon can not
both listen for connections on the same port.
You can either deactivate the regular sshd before starting gsisshd or
change the configuration of gsisshd to use a different port than the
standard ssh port number 22. Common choices for an alternative port
number are 23, 222 or 2222.
If you configure gsisshd to only accept gsi connections and not accept
other types of connections that require the existence of the ssh host
keys, you can turn off the generation of these keys in
/etc/sysconfig/gsisshd.