pylint: Fixing pylint errors and warnings

pylint: Fixing pylint errors and warnings

All python files must reach pylint score 10/10. This will be
regularly verified by Jenkins jobs to keep constant code quality.
VSPERF specific pylintrc file was updated according to the vsperf
coding standards. Distro version included in reports will be
slightly different, due to migration to new python package distro.
Previously used platform.distro() will be deprecated since python 3.7.

JIRA: VSPERF-487

Change-Id: I934120208b9624787a3567ccaa49e14d77d7a5bf
Signed-off-by: Martin Goldammer <martinx.goldammer@intel.com>
Reviewed-by: Martin Klozik <martinx.klozik@intel.com>
Reviewed-by: Al Morton <acmorton@att.com>
Reviewed-by: Christian Trautman <ctrautma@redhat.com>
Reviewed-by: Bill Michalowski <bmichalo@redhat.com>
Reviewed-by: Antonio Fischetti <antonio.fischetti@intel.com>
Reviewed-by: Sridhar Rao <sridhar.rao@spirent.com>