Clean up imports in bkr.server.authentication

Change-Id: I8e7c86d61a7e2d399dae94ac45a598f73eae8881
Clean up imports in bkr.server.configuration

Change-Id: Ia076f963a88f4c13f84c64ca36309e344fddb713
Merge "Clean up imports in bkr.server.authentication" into develop
Merge "Clean up imports in bkr.server.configuration" into develop