(PUP-2364) Use the the puppet config vardir setting

instead of the beaker variable puppetvardir.  This change, while
pleasing in and of itself, was needed for testing on AIX.  The vardir
used there by puppet is different, and Beaker does not track a separate
set of defaults for AIX.
Merge branch 'pup_2364_spike_vars' into stable

* pup_2364_spike_vars:
  (PUP-2364) Use the the puppet config vardir setting