(PUP-3277) Use owner from puppet settings rather than beaker defaults

The beaker host['user'] default setting is root, but the actual user
setting from puppet defaults is likely to be puppet or pe-puppet.  By
using the puppet settings, we are more likely to stay in sync with how
the files are being set by packaging or managed by puppet or supporting
puppetlabs modules.  This should cut down on spurious changes to
environment owner/modes that were cropping up in some pe test runs.
(PUP-3277) Ensure agents re-enabled after disable agent test

And a step in the agent_disable_lockfile step to ensure that agents are
re-enabled. This should insulate subsequent tests from a failure partway
through agenet_disable_lockfile leaving disabled agents in its wake.
Merge branch 'issue/stable/pup-3277-envdir-perms' into stable

* issue/stable/pup-3277-envdir-perms:
  (PUP-3277) Ensure agents re-enabled after disable agent test
  (PUP-3277) Use owner from puppet settings rather than beaker defaults