(PUP-3277) Use classifier when testing enc response

The current test sets up an enc instance for foss, but when running
against pe, it fails because the pe node_terminus configuration is in
[master] not [main].  We could adjust that, but then we
are not testing against a real PE environment, so instead, use the
classifier.
Merge branch 'issue/master/pup-3277-enc-non-existent-directory-environment-test-uses-classifier-in-pe'

* issue/master/pup-3277-enc-non-existent-directory-environment-test-uses-classifier-in-pe:
  (PUP-3277) Use classifier when testing enc response