UBUNTU: SAUCE: shiftfs: setup correct s_maxbytes limit

UBUNTU: SAUCE: shiftfs: setup correct s_maxbytes limit

BugLink: https://bugs.launchpad.net/bugs/1849482
Set the s_maxbytes limit to MAX_LFS_FILESIZE.
Currently shiftfs limits the maximum size for fallocate() needlessly
causing calls such as fallocate --length 2GB ./file to fail. This
limitation is arbitrary since it's not caused by the underlay but
rather by shiftfs itself capping the s_maxbytes. This causes bugs such
as the one reported in [1].

[1]: https://github.com/lxc/lxd/issues/6333
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Connor Kuehl <connor.kuehl@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>