If you are installing Salt via git/pip, the formula will try to overwrite your
install with packaged versions. This setting makes it possible to avoid that.
New versions of Salt put config files in /etc/salt/{minion,master}.d. We don't
want to erase them by using a clean: True on the file.recurse. This is a
backward incompatible change, but it's necessary to avoid deleting Salt config
files.
Resolves#104
