Fix SpaceAfterComma handling of trailing spaces

The `SpaceAfterComma` linter had a bug where it would incorrectly report
a lint for commas which had one or more trailing spaces followed by a
newline.

Fix it by ignoring the space count if the final character is a newline.

Change-Id: Ie0c353e9bd4c31514cd6b320fe8b4dc2b39eb1fd
Reviewed-on: http://gerrit.causes.com/40954
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>