add ATLAS_CHECK_THREAD_SAFETY to TrkGaussianSumFilter

Add ATLAS_CHECK_THREAD_SAFETY the package was migrated some time ago

This merge request affects 1 package:

• Tracking/TrkFitter/TrkGaussianSumFilter

added Egamma Tracking master review-pending-level-1 labels

CI Result SUCCESS

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available at NICOS MR-22656-2019-04-14-03-27
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 2
For experts only: Jenkins output [CI-MERGE-REQUEST 37031]

I approve the MR. Baida L1

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

merged

mentioned in commit 69171db3

added sweep:ignore label