Lock mutex when writing/reading newNodeConfigurations   - fix error when multi-threads client is calling "refresh" and     "applyConfiguration" at the same time.
Lock mutex when writing/reading newNodeConfigurations
  - fix error when multi-threads client is calling "refresh" and
    "applyConfiguration" at the same time.

pFernbach/gepetto-viewer-corba,Mathieu-Geisert/SceneViewer-corba,pFernbach/gepetto-viewer-corba,Mathieu-Geisert/SceneViewer-corba