Use libnss-unknown library to fake unknown uids
libnss-unknown is a small NSS module to gracefully handle unknown uids It is used in our Jenkins setup in scenarios where if the Jenkins UID is different than then entries inside the container image
For details, see: https://phabricator.apertis.org/T5385
Signed-off-by: Ritesh Raj Sarraf ritesh.sarraf@collabora.com