(TK-31) Fix bug with large cookie on a proxy request

I've doubled the size of the Request buffer from its default value for the HTTP Client created on a proxy request, as it was overflowing when given a very large cookie. 
@camlow325 The reason I did this was for readability. Without the wrapping string, this line would have been extremely long, but the wrapping string lets me limit it to 80 characters per line so that no single line gets too long.