use config instead of App.instance to propagate notebook_dir

Should behave more logically (I hope).

IPython/html/notebookapp.py

@@ -530,6 +530,10 b' class NotebookApp(BaseIPythonApplication):'
             except:
                 raise TraitError("Couldn't create notebook dir %r" % new)
         
+        # setting App.notebook_dir implies setting notebook and kernel dirs as well
+        self.config.FileNotebookManager.notebook_dir = new
+        self.config.MappingKernelManager.root_dir = new
+        
 
     def parse_command_line(self, argv=None):
         super(NotebookApp, self).parse_command_line(argv)

IPython/html/services/kernels/kernelmanager.py

@@ -42,18 +42,6 b' class MappingKernelManager(MultiKernelManager):'
     kernel_argv = List(Unicode)
     
     root_dir = Unicode(getcwd(), config=True)
-    def _root_dir_default(self):
-        from IPython.html.notebookapp import NotebookApp
-        if NotebookApp.initialized():
-            try:
-                app = NotebookApp.instance()
-            except Exception:
-                # can raise MultipleInstanceError, ignore
-                pass
-            else:
-                return app.notebook_dir
-            return app.notebook_dir
-        return getcwd()
 
     def _root_dir_changed(self, name, old, new):
         """Do a bit of validation of the root dir."""

IPython/html/services/notebooks/filenbmanager.py

@@ -47,17 +47,6 b' class FileNotebookManager(NotebookManager):'
         """
     )
     notebook_dir = Unicode(getcwd(), config=True)
-    def _notebook_dir_default(self):
-        from IPython.html.notebookapp import NotebookApp
-        if NotebookApp.initialized():
-            try:
-                app = NotebookApp.instance()
-            except Exception:
-                # can raise MultipleInstanceError, ignore
-                pass
-            else:
-                return app.notebook_dir
-        return getcwd()
     
     def _notebook_dir_changed(self, name, old, new):
         """Do a bit of validation of the notebook dir."""