Emacs completion produces duplicate prefixes when Jedi is disabled

[brandonwillard]

In an IPython session started with ipython --quick at 4f98f10

ip = get_ipython()
c = ip.Completer
ip.ex("class TestClass():\n\ta=1\n\ta1=2")
ip.Completer.use_jedi = False
c.all_completions("TestClass.a")

yields

['TestClass.TestClass.a', 'TestClass.TestClass.a1']

The expected output is ['TestClass.a', 'TestClass.a1']. The current output ruins Emacs completion when jedi is disabled.