[XFS] remove xfs_log_ticket_zone on rmmod

Fix bug introduced in commit eb01c9cd aka
"[XFS] Remove the xlog_ticket allocator"

SGI-PV: 980887
SGI-Modid: xfs-linux-melb:xfs-kern:30995a

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David Chinner <dgc@sgi.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>