[FIX] multicompany security

the rma module had company_id fields on rma.order and rma.order.line but not on rma.operation,
and no global multicompany record rules.

-> we fix this and avoid a mess with people allowed to see an operation in the drop down list
but unable to use it because if points to a warehouse of another company

rma/models/rma_operation.py

@@ -75,3 +75,7 @@ class RmaOperation(models.Model):
         comodel_name='rma.order.line', inverse_name='operation_id',
         string='RMA lines',
     )
+    company_id = fields.Many2one(
+        comodel_name='res.company', string='Company', required=True,
+        default=lambda self: self.env.user.company_id
+    )