Bug 3869: Fixed ShardedDOMDataTree to adhere to API

Bug 3869: Fixed ShardedDOMDataTree to adhere to API

ShardingTableEntry:
 - Replaced emptyMap with HashMap to allow to populate
   table entry
 - Fixed #remove(Iterator) to remove registration

ShardedDOMWriteTransaction:
 - Checks if writen path is delegated to other child
   producer.
 - submit() invokes DOMDataTreeProducer in order
   to notify when transaction is submitted.

ShardedDOMDataTreeProducer
 - #transactionSubmitted() clears openTx field
   in order to allow to allocate next transaction
   or close producer.

Added unit tests which tests ShardedDOMDataTree
to adhere to Shard & Producer API contracts defined
in DOMDataTreeService and DOMDataTreeProducerService

Change-Id: I39fae5f40e5b8a1cd07fcbe183c937b5c5bda348
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>
Signed-off-by: Robert Varga <rovarga@cisco.com>