There appear to be timing issues for the diag requests. Somehow, we're sending
out-of-date diagnostics and then not updating the UI when things change.
That needs to be fixed.
The problem was that when you start vim like "vim foo.cc", the FileReadyToParse
event is sent to the server before it's actually started up. Basically, a race
condition.
We _really_ don't want to miss that event. For C++ files, it tells the server to
start compiling the file.
So now PostDataToHandlerAsync in BaseRequest will retry the request 3 times
(with exponential backoff) before failing, thus giving the server time to boot.
These happen rarely and are not a big deal when they do. We still log them to
the Vim message area, but we don't annoy the user with the default, in-your-face
Python traceback.
