EX-9611 lipe: ignore pylint warnings

EX-9611 lipe: ignore pylint warnings

The Python-based lipe code is deprecated, but fails during
building because of newer pylint warnings.  Ignore errors
from pylint during building until someone fixes them.

Make the installation of pylint optional to simplify builds.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ibd94f6ef5ef69b1fd597f40bbecca6e3c3fb8f02
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/54861
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Feng Lei <flei@whamcloud.com>