It needs to be root in order to set the ownership and permissions on the
directories that are under /var/lib/lorax/composer/
Refactor the directory creation into a utility function, and use a umask
of 0o006 to ensure that the parent directories created do not have o+rw
set on them (makedirs behavior is different between Python 3.6 and 3.7
so umask of 0 doesn't work consistently).
This no longer uses the enabled configuration setting to select repos to
use. It uses everything in the repo_dir, and if system repos have not
been disabled it copies them into the repo_dir at startup, overwriting
the previous copy.
