Fix test_contrib_s3_core unit test

When running the full suite of run_tests.sh the test_contrib_s3_core tests run
fine, however when run standalone the tests fail

Change-Id: I287d05aaab40f441dca9fdca0a5dc6bee1fd073d
Fixes: bug #1120896
Merge "Fix test_contrib_s3_core unit test"