Reformat Robot files to follow best practices

Best practices in Robot files consist in using three spaces as
separator and not using tabs. This change updates all files
and includes the checking of the format as part of
`devops-stages/stage-test.sh`. In addition, it checks that files
have no CRLF terminators.

Change-Id: Ie71c2dd92585eba3baf98df0be54f05828819ad8
Signed-off-by: garciadeblas <gerardo.garciadeblas@telefonica.com>