Test helloworld-tcpclient fails to download hello.txt

The test helloworld-tcpclient fails to download the file it is expecting when running on a frdm-k64f board.

Console output:

```
{{start}}
TCP client IP Address is 192.168.1.62
Starting DNS lookup for mbed.org
DNS Response Received:
mbed.org: 212.95.239.234
Connecting to 212.95.239.234:80
Connected to 212.95.239.234:80
Sending HTTP Get Request...
HTTP Response received.
HTTP: Received 226 chars from server
HTTP: Received 200 OK status ... [FAIL]
HTTP: Received 'Hello world!' status ... [FAIL]
HTTP: Received message:

HTTP/1.1 301 Moved Permanently
Date: Fri, 14 Aug 2015 18:40:48 GMT
Server: Apache/2.2.22 (Ubuntu)
location: http://www.mbed.org/assets/uploads/hello.txt
Vary: Accept-Encoding
Content-Length: 0
Content-Type: text/html

{{failure}}
{{end}}
```