This patch fixes a long-standing bug in iscsit_build_conn_drop_async_message()
where during ERL=2 connection recovery, a bogus conn_p pointer could
end up being used to send the ISCSI_OP_ASYNC_EVENT + DROPPING_CONNECTION
notifying the initiator that cmd->logout_cid has failed.
The bug was manifesting itself as an OOPs in iscsit_allocate_cmd() with
a bogus conn_p pointer in iscsit_build_conn_drop_async_message().