/usr/lib/x86_64-linux-gnu/glusterfs/3.8.8/xlator/features/posix-locks.so is in glusterfs-common 3.8.8-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/glusterfs/3.8.8/xlator/features/locks.so