[DLM] fix aborted recovery during node removal

Red Hat BZ 211914

With the new cluster infrastructure, dlm recovery for a node removal can
be aborted and restarted for a node addition.  When this happens, the
restarted recovery isn't aware that it's doing recovery for the earlier
removal as well as the addition.  So, it then skips the recovery steps
only required when nodes are removed.  This can result in locks not being
purged for failed/removed nodes.  The fix is to check for removed nodes
for which recovery has not been completed at the start of a new recovery
sequence.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>