Fix tst_msgpackiodevice assertions
Fix tst_msgpackiodevice assertions

The tst_msgpackiodevice was missing an assertion when calling
listen(). Also the hasPendingConnection() was systematically
failing on Mac OS X 10.10 - replaced it with a SignalSpy for
the newConnection signal.

equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt,equalsraf/neovim-qt