Coerce the weird test env for MFHD into working inside buildbot

Coerce the weird test env for MFHD into working inside buildbot

'use testlib.pm' throws the standard "prove --lib lib -r t" recipe for testing
Perl packages out the window, so we have to override the Perl testing class
and point to the known location of testlib.pm

This may still fail for Evergreen branches prior to rel_2_1, but it's
_something_. Throw me a bone, here, will ya?

Ultimately, the best thing to do is probably to make MFHD tests conform.

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@2188 9efc2488-bf62-4759-914b-345cdb29e865