Change Select2Choice#convertInput() to use getRawInput()

[ageery]

The Select2Choice#renderInitializationScript method calls hasRawInput(), which checks FormControl#rawInput. If there is raw input, Select2Choice then calls Select2Choice#convertInput(). Rather than using FormControl#getRawInput, it uses

getWebRequest().getRequestParameters().getParameterValue(getInputName())

This doesn't work in a wizard. Instead of getting the parameters from the url, the code should just use the rawInput and parse it.