Revert "Excessive mutex locks were removed" and add missed defer

This reverts commit e65d6bd and adds missed defer call.

Signed-off-by: fubss <ivanlaish@gmail.com>

core/ledger/kvledger/kv_ledger.go

@@ -517,6 +517,8 @@ func (l *kvLedger) GetTransactionByID(txID string) (*peer.ProcessedTransaction,
 
 // GetBlockchainInfo returns basic info about blockchain
 func (l *kvLedger) GetBlockchainInfo() (*common.BlockchainInfo, error) {
+	l.blockAPIsRWLock.RLock()
+	defer l.blockAPIsRWLock.RUnlock()
 	bcInfo, err := l.blockStore.GetBlockchainInfo()
 	return bcInfo, err
 }
@@ -543,6 +545,8 @@ func (l *kvLedger) GetBlocksIterator(startBlockNumber uint64) (commonledger.Resu
 
 // GetBlockByHash returns a block given it's hash
 func (l *kvLedger) GetBlockByHash(blockHash []byte) (*common.Block, error) {
+	l.blockAPIsRWLock.RLock()
+	defer l.blockAPIsRWLock.RUnlock()
 	block, err := l.blockStore.RetrieveBlockByHash(blockHash)
 	return block, err
 }
@@ -1020,6 +1024,8 @@ func (itr *blocksItr) Next() (commonledger.QueryResult, error) {
 	if err != nil {
 		return nil, err
 	}
+	itr.blockAPIsRWLock.RLock()
+	defer itr.blockAPIsRWLock.RUnlock()
 	return block, nil
 }