Update function comment.
Update function comment.

* serf/serf.h
  (serf_request_bucket_request_create): Fix doc-string, function doesn't set
   the User-Agent header.
liuzongquan/serf,blueszhangsh/serf,krime/serf,Manouchehri/serf,blueszhangsh/serf,idomon/serf,wzugang/serf,sworda/serf,idomon/serf,wzugang/serf,liuzongquan/serf,Manouchehri/serf,justinweb/serf,blueszhangsh/serf,krime/serf,muthusuba/serf,sworda/serf,sworda/serf,Manouchehri/serf,idomon/serf,wzugang/serf,idomon/serf,justinweb/serf,Manouchehri/serf,wzugang/serf,TommyU/serf,sworda/serf,TommyU/serf,justinweb/serf,blueszhangsh/serf,krime/serf,justinweb/serf,TommyU/serf,muthusuba/serf,liuzongquan/serf,krime/serf,muthusuba/serf,liuzongquan/serf,muthusuba/serf,TommyU/serf