filer: remove replication, collection, disk_type info from entry metadata

these metadata can change and are not used

weed/filer/entry.go

@@ -15,10 +15,7 @@ type Attr struct {
 	Uid           uint32      // owner uid
 	Gid           uint32      // group gid
 	Mime          string      // mime type
-	Replication   string      // replication
-	Collection    string      // collection name
 	TtlSec        int32       // ttl in seconds
-	DiskType      string
 	UserName      string
 	GroupNames    []string
 	SymlinkTarget string