HPCC-11565 Avoid calls to SDS manager for dangling connections

If SDS connections still exist and are destroyed after the SDS
manager is destroyed a crash ensues. Avoid this by spotting the
connection is 'orphaned' and issue a warning instead.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #5980 from jakesmith/hpcc-11565

HPCC-11565 Avoid calls to SDS manager for dangling connections

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>