[ATR-21197] Legacy TrigCost Python3 compatibility

Replaces uses of removed has_key function.

This merge request affects 1 package:

• Trigger/TrigMonitoring/TrigCostMonitor

added DQ Trigger master review-pending-level-1 labels

CI Result SUCCESS (hash 4e66cc29)

	Athena	AthSimulation	AnalysisBase	AthGeneration
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
AnalysisBase: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 17050]

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

merged

mentioned in commit 105e743f

added sweep:ignore label