try to shutdown at the end of every notebook run
try to shutdown at the end of every notebook run

this line causes noise in the test suite, but if we just ignore it,
we'll never get to the bottom of it. It seems to only happen when
running 'iptest js', and *not* when running the 'casperjs test' command
directly, with a notebookserver that was launched manually.

ipython/ipython,ipython/ipython