rietveld: Make upload.py's GetRpcServer() take explicit params.
rietveld: Make upload.py's GetRpcServer() take explicit params.

This function does some work to detect dev_appserver that git-cl
needs; we get prompted for a username and password otherwise.
I have a separate change to git-cl to make it use this function
instead of constructing a server object directly.

Patch by Dan Erat <derat@chromium.org>

Review URL: http://codereview.chromium.org/1635002

git-svn-id: 095a516e186c72f46b708383d0d3f28c2432e8a1@520 e30e9e8f-1b4c-0410-881d-6f13584adfe0

imirkin/rietveld,imirkin/rietveld