Revert mongo authentication
At the beginning, it appeared only to be broken on RHEL 6, but now it does not seem to function reliably on RHEL 7. Subsequent runs of the installer will generate a bunch of non-fatal errors.
Because of https://tickets.puppetlabs.com/browse/MODULES-534, it seems, which remains unfixed for quite some time. It seems clear to me know why auth is false by default in this thing, the module is really flaky.
Since we're planning to drop mongo in a future release anyway, I think it's best just to leave it off on el6 and el7 now too.