HCatalog should use IMetaStoreClient interface

Hive uses IMetaStoreClient and it makes using RetryingMetaStoreClient easy. Hence during a failure, the client retries and possibly succeeds. But HCatalog has long been using HiveMetaStoreClient directly and hence failures are costly, especially if they are during the commit stage of a job. Its also not possible to do rolling upgrade of MetaStore Server.