(#18308) Use argv in Facter::Application.parse
Add tests for Facter::Application.parse
terge branch 'tobyhs-ticket/1.6.x/18308_application_parse_argv' into 1.6.x

* tobyhs-ticket/1.6.x/18308_application_parse_argv:
  Add tests for Facter::Application.parse
  (#18308) Use argv in Facter::Application.parse