Remove copyright from empty files

According to policy change in HACKING:
http://docs.openstack.org/developer/hacking/#openstack-licensing
empty files should no longer contain copyright notices.

This patch aslo changes files in ironic/openstack/common, which
were changed in oslo https://review.openstack.org/#/c/64082/

Change-Id: I85fdbc2d94200b6e47ad7c9b8717d4578de2eaee
Closes-Bug: #1262424
Merge "Remove copyright from empty files"