[FAB-9733] Add Done() to State interface

This change set adds a Done() method to the state interface, so that
the underlying Query executor could be released.

Change-Id: I6d10b8557b56b6a56bd108c295d4b0e5a08a309f
Signed-off-by: yacovm <yacovm@il.ibm.com>

Author: yacovm

core/handlers/endorsement/api/state/state.go

@@ -21,6 +21,9 @@ type State interface {
 
 	// GetTransientByTXID gets the values private data associated with the given txID
 	GetTransientByTXID(txID string) ([]*rwset.TxPvtReadWriteSet, error)
+
+	// Done releases resources occupied by the State
+	Done()
 }
 
 // StateFetcher retrieves an instance of a state

core/handlers/validation/api/state/state.go

@@ -21,6 +21,9 @@ type State interface {
 	// can be supplied as empty strings. However, a full scan should be used judiciously for performance reasons.
 	// The returned ResultsIterator contains results of type *KV which is defined in protos/ledger/queryresult.
 	GetStateRangeScanIterator(namespace string, startKey string, endKey string) (ResultsIterator, error)
+
+	// Done releases resources occupied by the State
+	Done()
 }
 
 // StateFetcher retrieves an instance of a state