Improve output of test.py

Previously you got for both syntax and niceness checks:
Validating files...
Validation passed, validated 3 files.

Now we get different messages like:
Checking syntax of xml files...
Check passed, validated 3 xml files.

Checking niceness of xml files...
Check passed, validated 3 xml files.

Change-Id: I5bb0b014b743826094aae274fa730eb73ba1621e
Merge "Improve output of test.py"