ceph/005: verify correct statfs behaviour with quotas

ceph/005: verify correct statfs behaviour with quotas

When using a directory with 'max_bytes' quota as a base for a mount,
statfs shall use that 'max_bytes' value as the total disk size.  That
value shall be used even when using subdirectory as base for the mount.

A bug was found where, when this subdirectory also had a 'max_files'
quota, the real filesystem size would be returned instead of the parent
'max_bytes' quota value.  This test case verifies this bug is fixed.

Signed-off-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>