Align license headers with REUSE guidelines

Align license headers with REUSE guidelines

This patch applies a consistent use of license and copyright
headers to all source files according to the guidelines of
REUSE.

Signed-off-by: Georg Kunz <georg.kunz@ericsson.com>
Change-Id: I8973efe304e8fb03ad0861d4b8356221d898d548
Reviewed-on: https://gerrit.opnfv.org/gerrit/c/kuberef/+/72804
Reviewed-by: Michael Pedersen <michaelx.pedersen@intel.com>
Tested-by: jenkins-ci <jenkins-opnfv-ci@opnfv.org>