I am unsure why you are doing it this way specifically, maybe I am not understanding.

But my solution would be to make the field on the model in python as:

x_saluation_test = fields.Selection([("herr", "Herr"), ("frau", "Frau")], string="my selection", default="herr")

Then on the view you just need to put <field name="x_saluation_test"/> and it will create the selection widget for you. 

Also, use the "default" parameter to select a default value. 

I hope this helps.