replicainstall: Unify default.conf file creation
In domain level 0, the default.conf file was created using just
file operations. Unified this with domain level 1 where IPAChangeConf
is used.
Also moved the creation of the file to promote_check in DL1.
https://fedorahosted.org/freeipa/ticket/6392
Reviewed-By: Martin Basti <mbasti@redhat.com>