incomplete response when using mode=grpcwebtext

When using mode=grpcwebtext for client configuration, responses are giving an error:

`{code: StatusCode.UNKNOWN, message: 'Incomplete response'}`

The response is received by the client, but is truncated (e.g. string should be 'hello world' but is 'hello'). This error does not occur when using mode=grpcweb. I'm unsure if additional configuration is needed to use grpcwebtext, but following the grpc-web examples it does not seem like it.

It looks like this may be related to https://github.com/grpc/grpc-web/pull/903 and issue https://github.com/grpc/grpc-web/issues/881