Refs #8374 SNSPowderRedux no longer leaves files behind

Implemented cleanup in SNSPowderRedux.py, removing all the files it leaves behind.
Refs #8374 LOQAddBatch no longer leaves files behind

Implemented cleanup in LOQAddBatch.py, removing all the files it leaves behind.
Refs #8374 Diffraction_Workflow_Test no longer leaves files behind

Implemented cleanup in Diffraction_Workflow_Test.py, removing all the files it leaves behind.