[FIX] sale_stock: default warehouse_id

Finetuning of
https://github.com/odoo/odoo/commit/b30e280b2d676f16873ac0fd1279c4870d994dec


:

self.user_id is always an empty recordset in a default function call,
use self.env.user instead, it is the default value for user_id.

The _init_column override is needed to ensure the new property field on
res_users isn't read at module installation, because its ir.model.fields
doesn't exist already, leading to a wrong sql query in ir_property.

closes odoo/odoo#48378

X-original-commit: 6c6bd018c761535f973781319090116d7eea60ad
Signed-off-by: Victor Feyens (vfe) <vfe@odoo.com>