Add file name to whitespace information

Previously you got:
  trailing or unnecessary whitespaces in following lines: 375
  trailing or unnecessary whitespaces in following lines: 33, 117

Now you get:
file openstack-network-connectivity-admin/ch_config.xml:
  trailing or unnecessary whitespaces in following lines: 375
file openstack-user/src/section_nova_cli_floating_ips.xml:
  trailing or unnecessary whitespaces in following lines: 33, 117

Change-Id: Idebbc06cfcaf44e8c4cce0a14b60b07bcb6e648e
Merge "Add file name to whitespace information"