Allow empty Reason-Phase in the Status-Lines, which is allowed by rtf

Allow empty Reason-Phase in the Status-Lines, which is allowed by rtf
http://www.w3.org/Protocols/rfc2616/rfc2616.html .
Fixed by removing a space which will now be visibly in the errormessages,
but as this errors should never happen anyway and an extra space doesn't
harm we don't removed it.

  * methods/http.cc:
    - allow empty Reason-Phase in Status-Line to please squid,
      thanks Modestas Vainius for noticing! (Closes: #531157, LP: #411435)