(PUP-3459) Pre-suite puppet bug workaround to avoid permissions errors during acceptance test.

The issue is that `puppet apply` on its first run will create (for the FOSS case) `/var/lib/puppet/reports`. If the process belongs to `root` user then `/var/lib/puppet/reports` will belong to `root` and subsequently be unwritable by the puppet user itself.

This workaround basically ensures that during the first run of `puppet apply` the process will be owned by the puppet user, which then meands `/var/lib/puppet/reports` will also belong to the puppet user. 

This is necessary because in `acceptance/suites/pre_suite/foss/85_configure_sut.rb` we must call `puppet apply` as `root` in order to modify `/etc/hosts` to stub `updates.puppetlabs.com`. @camlow325 brought this to my attention because he was noticing permission denied messages on `puppet {agent,apply}` runs on the master when he was looking through the Beaker output on some tests.

I chose to run `puppet apply` as the puppet user rather than running `chown` on the reports directory in the latter pre_suite step to catch any other directories that might be created programmatically by puppet. I think the number of such directories has been minimized now since @haus and I addressed a similar bug that was actually causing acceptance test failures a month or so ago.