iotests: ignore import warnings from pylint

iotests: ignore import warnings from pylint

The right way to solve this is to come up with a virtual environment
infrastructure that sets all the paths correctly, and/or to create
installable python modules that can be imported normally.

That's hard, so just silence this error for now.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20200331000014.11581-4-jsnow@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>