Fix case when buggy mjpeg servers set the boundary header without the two hyphen characters.

According to http://tools.ietf.org/html/rfc2046:

   The Content-Type field for multipart entities requires one parameter,
   "boundary". The boundary delimiter line is then defined as a line
   consisting entirely of two hyphen characters ("-", decimal value 45)
   followed by the boundary parameter value from the Content-Type header
   field, optional linear whitespace, and a terminating CRLF.
Remove unneeded parenthesis.
Last test always fails, removed