Preventing Vim thread block on file save

Syntastic would run SyntasticCheck on file save, which would unconditionally
call _latest_file_parse_request.Response() and thus block until the request
returned from the server. We don't want that, so we throw in an explicit check
for the request being ready.

python/ycm/youcompleteme.py

@@ -172,7 +172,7 @@ class YouCompleteMe( object ):
 
 
   def GetDiagnosticsFromStoredRequest( self ):
-    if self._latest_file_parse_request:
+    if self.DiagnosticsForCurrentFileReady():
       to_return = self._latest_file_parse_request.Response()
       # We set the diagnostics request to None because we want to prevent
       # Syntastic from repeatedly refreshing the buffer with the same diags.