Update log file diff in post.sh

Prior to this change log file diffs in unit tests compared the reference file to the current output, rather than the other way around, so that lines in the log removed due to local changes are marked with a + in the diff output and lines added to the log are marked with a -.

This commit switches the order of comparison with the aim of making the output more intuitive. See discussion in ATEAM-644.

Closes ATEAM-644

This merge request affects 1 package:

• AtlasTest/TestTools

added Test master review-pending-level-1 labels

CI Result SUCCESS (hash 93006460)

	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 19163]

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

mentioned in commit c4a42c0b

merged

added sweep:ignore label

mentioned in merge request !28950 (merged)