Fix missing space in get_gateway kopt

There is a missing space in the netcfg/get_gateway line in
cobbler.yaml.  For most users this causes no impact since this data
isn't used by default.  However for advanced users that want to
call the cobbler class directly instead of going through puppet-coi
(which removes substantial other functionality), this causes two
kopts to run together.

Closes-Bug: #1269126