EventPrimitives: Fix cppcheck warnings.

Pass class instances by const reference, not by value.

This merge request affects 1 package:

• Event/EventPrimitives

Adding @rbianchi as watcher

added EDM master review-pending-level-1 labels

CI Result SUCCESS (hash d6ff689e)

	Athena	AthSimulation	AthGeneration	AnalysisBase
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
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 19363]

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

merged

mentioned in commit 2c424932

added sweep:ignore label