HPCC-11380 - Move SDS base 'state' to client class

A state flag only used by the client derivitive of the SDS
tree, was declared in the base class, thereby existing in
the server derivitive too.
Moving to client only, will save a little space.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #5831 from jakesmith/hpcc-11380

HPCC-11380 - Move SDS base 'state' to client class

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>