jfs: return f_fsid for statfs(2)

This patch makes jfs return f_fsid info for statfs(2). By Andreas'
suggestion, this patch populates a persistent f_fsid between boots/mounts
with help of on-disk uuid record.

Signed-off-by: Coly Li <coly.li@suse.de>
Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>