Fix retried requests

[jstamerj]

When first creating a request, this.options.data is converted to a string (if it's not already a string). That string is then converted to a buffer and transmitted as the request body.
When retrying a request, that buffer was stringified, then this string was converted to another buffer. The retry request body then looks bogus (like '0=123&1=34&2=105&3=100&4=34' ...)
The content-type header was also trounced with the value 'application/x-www-form-urlencoded'.

This fix puts the Buffer data in a different variable and prevents the data from being re-stringified and re-bufferified when when retry() is called.

[easternbloc]

Hi, this needs a rebase before I can take a look.

Also any chance you can write some tests for this?

[shannonchou]

Yeah, I faced the same problem. It seems that the request body is invalid after calling retry(). I paste a log snippet below.

ESC[32m[2014-10-27 17:08:39.730] [INFO] [default] - ESC[39mdid not return within 30000 ms, retry it
ESC[32m[2014-10-27 17:08:52.461] [INFO] [default] - ESC[39msend Hipchat unsuccessfully, return: {"error":{"code":400,"message":"The request requires a properly encoded body with the 'content-type' header set to '['application/json']","type":"Bad Request"}}