xAODEgammaAthenaPool: Add tests for reading old data.

Add tests to verify backwards compatibility by reading old data files.

This merge request affects 1 package:

• Event/xAOD/xAODEgammaAthenaPool

Adding @rbianchi as watcher

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

CI Result SUCCESS

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available at NICOS MR-26777-2019-09-24-20-54
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 3555]

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

merged

mentioned in commit f826c21e

added sweep:ignore label