ceph: don't check quota for snap inode

ceph: don't check quota for snap inode

BugLink: https://bugs.launchpad.net/bugs/1875884
snap inode's i_snap_realm is not pointing to ceph_snap_realm.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit 2596366907f872de7be0557720bb55bccf7489d9)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Sultan Alsawaf <sultan.alsawaf@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>