Add even more debug output to tst_files.

The test blocks CI sadly nobody can reproduce the failure locally. This
change is extension to c416ada9bebed82c9859882da14078222354c0d4

Change-Id: I00fd29286a2ea35c4dbb2396471d471ddc94882b
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>