ocfs2: fix double kmem_cache_destroy in dlm_init

In dlm_init, if create dlm_lockname_cache failed in
dlm_init_master_caches, it will destroy dlm_lockres_cache which created
before twice.  And this will cause system die when loading modules.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/dlm/dlmmaster.c

@@ -472,11 +472,15 @@ bail:
 
 void dlm_destroy_master_caches(void)
 {
-	if (dlm_lockname_cache)
+	if (dlm_lockname_cache) {
 		kmem_cache_destroy(dlm_lockname_cache);
+		dlm_lockname_cache = NULL;
+	}
 
-	if (dlm_lockres_cache)
+	if (dlm_lockres_cache) {
 		kmem_cache_destroy(dlm_lockres_cache);
+		dlm_lockres_cache = NULL;
+	}
 }
 
 static void dlm_lockres_release(struct kref *kref)