Refactoring the code so that HiveTxnManager interface will support lock/unlock table/database object

This is just a refactoring step which keeps the current logic, but it exposes the explicit lock/unlock table and database in HiveTxnManager which should be implemented differently by the subclasses ( currently it's not. e.g., for ZooKeeper implementation, we should lock table and database when we try to lock the table).