reset leveldb batch after the commit

While committing data to leveldb in iteration, it is
necessary to reset the batch. Otherwise, we would be
appending entries and rewriting written entries in the
previous iteration.

Signed-off-by: Senthil Nathan N <cendhu@gmail.com>

core/ledger/pvtdatastorage/store.go

@@ -777,6 +777,7 @@ func (s *Store) purgeExpiredData(minBlkNum, maxBlkNum uint64) error {
 			batch.Delete(encodeMissingDataKey(missingDataKey))
 		}
 		s.db.WriteBatch(batch, false)
+		batch.Reset()
 	}
 	logger.Infof("[%s] - [%d] Entries purged from private data storage till block number [%d]", s.ledgerid, len(expiryEntries), maxBlkNum)
 	return nil
@@ -870,7 +871,7 @@ func (s *Store) processCollElgEvents() error {
 					collEntriesConverted++
 					if batch.Len() > s.maxBatchSize {
 						s.db.WriteBatch(batch, true)
-						batch = s.db.NewUpdateBatch()
+						batch.Reset()
 						sleepTime := time.Duration(s.batchesInterval)
 						logger.Infof("Going to sleep for %d milliseconds between batches. Entries for [ns=%s, coll=%s] converted so far = %d",
 							sleepTime, ns, coll, collEntriesConverted)