ENG-4713: Fix @LoadSinglepartitionTable dispatch if legacy hashinator is used.

Legacy hashinator hashes numbers and byte arrays differently, so passing the
partitioning parameter as a byte array will result in mispartitioned
transaction. Convert the byte array back to its origin object for hashing
purpose.
ENG-4713: Fix broken test in TestClientInterface.
ENG-4713: Address review comments from Izzy in ClientInterface.
Merge pull request #522 from VoltDB/ENG-4713

ENG-4713: Fix @LoadSinglepartitionTable dispatch if legacy hashinator is used