Revert "UBUNTU: SAUCE: (namespace) security/integrity: Harden against malformed xattrs"

Revert "UBUNTU: SAUCE: (namespace) security/integrity: Harden against malformed xattrs"

BugLink: https://bugs.launchpad.net/bugs/1644165
This reverts commit 038b77f6432ca631a3fdf4b9a5a7b217a9d8ec2e.

The kernel fix for bug #1634964 breaks LXD userspace, in particular the
following commits:

ac7f3f73cb39 (namespace) vfs: Don't modify inodes with a uid or gid unknown to the vfs
ca52383ad6a6 (namespace) vfs: Don't create inodes with a uid or gid unknown to the vfs

LXD 2.0.6 will include changes to support these kernel changes, but it isn't
available yet on xenial, so for now we just revert these commits.

Signed-off-by: Luis Henriques <luis.henriques@canonical.com>