r20599: - forward extended operations in the partitions module

r20599: - forward extended operations in the partitions module
- by default the operations goes to all partitions
- but some wellkown ones will go to just one partition
  (DSDB_EXTENDED_REPLICATED_OBJECTS_OID for now)

I'll soon change the partitions module so that it'll attach a
DSDB_CONTROL_PARTITION_CONTEXT_OID control to give
the repl_meta_data or other partition specific modules a chance to
to know for which partition it should work.

metze