Fix robot syntax with robot.tidy tool

- have to skip .robot files with the trailing-whitespace hook because
it will remove the blank line at the end of a file whereas robot tidy
will add one which causes a failure

This change is coming from using the latest RF and
robotframework-tidy-wrapper.

Signed-off-by: Jamo Luhrsen <jluhrsen@gmail.com>
Change-Id: I7ad30196d4ad3641901578614e3b417e4772498d