Allow API driven tests via install_and_test_tool_shed_repositories framework.
Greg/Dave - I don't have the infrastructure/knowledge to test this changeset, so sorry if it breaks something, but this is what I believe is nessecary if you want to set GALAXY_TEST_DEFAULT_INTERACTOR=api or if anyone posts a tool to the tool shed that forces the issue by marking a test case with 'interactor="api"'.