Refs #8374 HFIRBackgroundAPIv2 no longer leaves files behind

Implemented cleanup in all the tests contained in HFIRBackgroundAPIv2.py, removing all the files it leaves behind.
Refs #8374 HFIRTestsAPIv2 no longer leaves files behind

Implemented cleanup in HFIRTestsAPIv2.py, removing all the files it leaves behind.
Refs #8374 HFIREffAPIv2 no longer leaves files behind

Implemented cleanup in HFIREffAPIv2.py, removing all the files it leaves behind.
Refs #8374 HFIRReductionAPIv2 no longer leaves files behind

Implemented cleanup in HFIRReductionAPIv2.py, removing all the files it leaves behind.
Refs #8374 HFIRTransAPIv2 no longer leaves files behind

Implemented cleanup in HFIRTransAPIv2.py, removing all the files it leaves behind.
Refs #8374 Cleaned up code in HFIRTestsAPIv2 and HFIRBackgroundAPIv2

HFIRTestsAPIv2.py and HFIRBackgroundAPIv2.py have had their cleanup code imporved to follow better python practice and reduce repeated code.
Merge branch 'feature/8374_clean_up_tests' into develop