dlm: allow dlm do recovery during shutdown

If a node down event happens while dlm shutdown in progress, dlm recovery
should be done before dlm is shutdown.  We can't migrate unrecovered locks,
obviously.  But dlm_reco_thread only does recovery if the dlm_state is
in DLM_CTXT_JOINED.

dlm_reco_thread should do recovery if dlm_state is in DLM_CTXT_JOINED or
DLM_CTXT_IN_SHUTDOWN.

Signed-off-by: Srinivas Eeda <srinivas.eeda@oracle.com>
Signed-off-by: Joel Becker <joel.becker@oracle.com>