Toolbar Action Test Failure for WxPython on Linux and Windows

The `test_wx_toolbar_action` test works fine on OS X, but fails on Windows and Linux. For some reason the `wxEVT_COMMAND_TOOL_CLICKED` is not finding its way through all the code to actually perform the action. Not sure what proximate cause is, but this seems like a lower-level Pyface thing, and should be tested first there.

The test UI works as expected when run stand-alone and manually clicked.