test: Move stat-printing into its own function

test: Move stat-printing into its own function

Add a function to show the stats, so we can decide when to print it.

This slightly adjusts the output, so that any 'test not found' message
appears on its own line after all other output.

The 'failures' message now appears in lower case so update pytest
accordingly.

Signed-off-by: Simon Glass <sjg@chromium.org>