Allow seed values of bytes for bytes fields
Allow seed values of bytes for bytes fields

Summary: Thrift randomizer uses the StringRandomizer for bytes as well as utf-8 strings. The eval_seed method should allow bytes since that's what will be there.

Differential Revision: D16532649

fbshipit-source-id: 34234520c1e9bda30de1bc03e276307694fff6fc

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift