prevent db_api test from clobbering global name

One of the tests checks that we can rename the GLOBAL_GROUP_NAME,
but never reverts it to its original value. This causes future
tests to fail even though they shouldn't. This fix reverts
GLOBAL_GROUP_NAME after testing it can be changed.
Merge pull request #132 from bobbydavid/globaltest

prevent db_api test from clobbering global name