When the wrapper processes comps file, it wasn't emitting "default"
argument for groupid element. The default is false and most entries are
actually using the default, so let's only emit it if set to true.
Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1882358
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>