Eliminate redundant RPC call to get file information in HPath.

The HPath class makes 2 separate calls to FileSystem#getFileStatus to get the block size and replication. In the case of HDFS, this results in 2 separate but identical RPC transactions with the NameNode. The situation is the same for many other alternative FileSystem implementations too. We can get a minor latency improvement and lighten some RPC load on the remote services by using a single call and getting the block size and replication from the same response.