Delete obd_self_export from exp_obd_chain while we are disconnecting exports

during a forced cleanup.  Otherwise, we will end up pointing to work_list,
which is on the stack, and a list_del_init() on exp_obd_chain will end up
stomping on some innocent variable on the stack, ending its already-short
life just a bit too early.
b=2908
r=robert

lustre/ChangeLog

@@ -4,6 +4,7 @@ tbd  Cluster File Systems, Inc. <info@clusterfs.com>
 	- fixes for glimpse AST timeouts / incorrectly 0-sized files (2818)
 	- don't overwrite extent policy data in reply if lock was blocked (2901)
 	- drop filter export grants atomically with removal from device (2663)
+	- del obd_self_export from work_list in class_disconnect_exports (2908)
 
 2004-03-04  Cluster File Systems, Inc. <info@clusterfs.com>
        * version 1.2.0

lustre/obdclass/genops.c

@@ -630,6 +630,9 @@ void class_disconnect_exports(struct obd_device *obd, int flags)
                         CDEBUG(D_HA,
                                "exp %p export uuid == obd uuid, don't discon\n",
                                exp);
+                        /* Need to delete this now so we don't end up pointing
+                         * to work_list later when this export is cleaned up. */
+                        list_del_init(&exp->exp_obd_chain);
                         class_export_put(exp);
                         continue;
                 }