fix for #217

The tests now require the RADICAL_PILOT_TEST_DBNAME variable to be set in the
environment. This has been added to the unit tests.

For all practical purposes this works pretty well:

RADICAL_PILOT_TEST_DBNAME=rbtest_`date | md5`
Merge branch 'devel' of github.com-oleweidner:radical-cybertools/radical.pilot into devel