(PUP-3334) Fix issue around settings not updating with environment.conf

Prior to this commit, environment settings were not being updated
when environment.conf was changed, even if environment timeout had
expired. This was because they were being cached in places in
Puppet.settings that were not being cleared.

Now, all the cached data for a particular environment is cleared
when the environment timeout expires.
Typo here, so the path isn't being tested.  Which is scary in a false green kind of way, but that's the risk we take without another layer of tests testing our test helpers.  One way to check for this kind of thing, is to make sure you see a failure first.