ocfs2/dlm: fix memory leak of dlm_debug_ctxt

ocfs2/dlm: fix memory leak of dlm_debug_ctxt

dlm_debug_ctxt->debug_refcnt is initialized to 1 and then increased to 2
by dlm_debug_get in dlm_debug_init.  But dlm_debug_put is called only
once in dlm_debug_shutdown during unregister dlm, which leads to
dlm_debug_ctxt leaked.

Link: http://lkml.kernel.org/r/577BB755.4030900@huawei.com
Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Reviewed-by: Jiufei Xue <xuejiufei@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>