(PUP-1551) Use environmentpath in can_enumerate_environments test

Forgot to update the puppet.conf environmentdir setting to
environmentpath. Also change assert_not_match to assert_no_match call
in environmentpath test, as the later is the correct call. Not entirely
certain why this wasn't failing before.
Merge branch 'issue/master/pup-1551-fix-enumerate-env-test'

* issue/master/pup-1551-fix-enumerate-env-test:
  (PUP-1551) Use environmentpath in can_enumerate_environments test