[FIX] auth_password_policy: keep current policy on update

On update/upgrade we should keep current password policy if its
already set

closes odoo/odoo#137228

Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>

addons/auth_password_policy/data/defaults.xml

 <odoo>
-    <record model="ir.config_parameter" id="minlength">
+<data noupdate="1">
+    <record model="ir.config_parameter" id="minlength" forcecreate="True">
         <field name="key">auth_password_policy.minlength</field>
         <field name="value" type="int">8</field>
     </record>
+</data>
 </odoo>