Since keyboard navigation now works in Software Selection
(https://bugzilla.redhat.com/show_bug.cgi?id=1192155), we can now select
desired environment (e. g. minimal install) programmatically by going
through the list until desired environment is highlighted. This also
deals with bugs like https://bugzilla.redhat.com/show_bug.cgi?id=1177002.
This still selects only minimal install, but I think that it will
be easy to refactor when we will decide that we want to install other
environments as well.