FastSiDigitization: Fix cppcheck warnings.

Clean up use of member variable.

Build area was cleaned as per request posted in the DB. The full software build will be performed

This merge request affects 1 package:

• InnerDetector/InDetDigitization/FastSiDigitization

This merge request affects 2 files:

• InnerDetector/InDetDigitization/FastSiDigitization/FastSiDigitization/SCT_FastDigitizationTool.h
• InnerDetector/InDetDigitization/FastSiDigitization/src/SCT_FastDigitizationTool.cxx

Adding @jchapman ,@goetz ,@sroe as watchers

added Digitization InnerDetector master review-pending-level-1 labels

removed review-pending-level-1 label

added review-approved label

CI Result SUCCESS (hash 4dda6d6f)

	Athena
externals
cmake
make
tests

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Athena: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 62743]

merged

mentioned in commit 73788fba

added sweep:ignore label