Chunk server: remove redundant checksum vector clear() in chunk replicator.
Chunk server: fix replicator read checksum failure handling by always clearing read op io buffer before issuing chunk read.
Merge branch 'master' into topic/krb
Meta server: add user and group names to rpcs (lookup, lookup path, read dir plus, create, etc.) that respond with file attributes in the case if the client connection is "authenticated", i.e. authenticated id is valid. In order to minimize cpu and network bandwitdh only add user and group names that are unique, i.e. omit user and group names for entries where user and/or group names can be obtained from the previous entry with the same user and/or group id. The intention is to only "update" client's user and name mappings when new user or group id is encountered.