License: Wrap GPL block to 80 characters

The original license block was adapted from
https://wiki.fd.io/view/TSC/Proposed_Header_Python_Test_Scripts
resulting in a line longer than 80 chars,
but those are reported (although not blocked) by tox verify job.

As the text from wiki was not used in verbatim
(it uses c-style comment block),
minor formatting change like this should not be a big deal.

+ Bump copyright year.

Change-Id: I55e3a0232639b448b1a6d7b1f3af84d903a8d0a5
Signed-off-by: Vratko Polak <vrpolak@cisco.com>