Revert "UBUNTU: SAUCE: (namespace) fs: Allow superblock owner to change ownership...

Revert "UBUNTU: SAUCE: (namespace) fs: Allow superblock owner to change ownership of inodes"

BugLink: https://bugs.launchpad.net/bugs/1644165
This reverts commit 07053c83daff1bceffb3dcda7108eb0016bef3bf.

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>