Fix integration of puppet-arcanist

Summary:
rPPHAB69fc375c32a306af97d4371b7e1f1b5c28de2c1c introduced a regression: the
phabricator daemons would not run because pcntl functions were disabled.

Test Plan:
Automated tests were already catching failure. Added some new tests
which make the failure more clear and specific.

Reviewers: #macpros_internal, jbowman

Reviewed By: #macpros_internal, jbowman

Subscribers: jbowman

Differential Revision: http://phabricator.macprofessionals.lan/D31