Flake8 fixes for JetRec: ATLJETMET-1303

Chiefly removes unnecessary imports and unused variables.

This merge request affects 1 package:

• Reconstruction/Jet/JetRec

This merge request affects 9 files:

• Reconstruction/Jet/JetRec/CMakeLists.txt
• Reconstruction/Jet/JetRec/python/FastJetInterfaceConfig.py
• Reconstruction/Jet/JetRec/python/JetAlgorithm.py
• Reconstruction/Jet/JetRec/python/JetFlavorAlgs.py
• Reconstruction/Jet/JetRec/python/JetRecStandard.py
• Reconstruction/Jet/JetRec/python/JetRecStandardToolManager.py
• Reconstruction/Jet/JetRec/python/JetRecStandardTools.py
• Reconstruction/Jet/JetRec/python/JetRecUtils.py
• Reconstruction/Jet/JetRec/python/JetToolSupport.py

Adding @goetz as watcher

added JetEtmiss Reconstruction master review-pending-level-1 labels

CI Result FAILURE (hash 5149f11b)

	Athena	AthSimulation	AthGeneration	AnalysisBase	AthAnalysis
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
AnalysisBase: number of compilation errors 0, warnings 0
AthAnalysis: number of compilation errors 0, warnings 3
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 25760]

added review-user-action-required label

removed review-pending-level-1 label

AthAnalysis failures unrelated.

added review-pending-level-1 label and removed review-user-action-required label

Code changes look fine. Magdalena (L1)

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit d612c562

added sweep:ignore label