[IMP] mrp_bom_version: use new api correctly

mrp_bom_version/README.rst

@@ -6,7 +6,13 @@ MRP - BoM Version
 =================
 
 This module provides a state in the BoM whether to allow their use in
-manufacturing, to do the following states are defined:
+manufacturing.
+
+
+Usage
+=====
+
+The following states are defined:
 
 * **Draft**:
   The form will be available for data entry, and may move to "active" state.
@@ -31,9 +37,6 @@ to be unique.
   changing state to draft
 
 
-Usage
-=====
-
 .. image:: https://odoo-community.org/website/image/ir.attachment/5784_f2813bd/datas
    :alt: Try me on Runbot
    :target: https://runbot.odoo-community.org/runbot/129/8.0

mrp_bom_version/models/mrp_bom.py

@@ -78,10 +78,11 @@ class MrpBom(models.Model):
 
     @api.multi
     def button_draft(self):
-        self.ensure_one()
-        self.active = (self.company_id.active_draft if self.company_id else
-                       self.env.user.company_id.active_draft)
-        self.state = 'draft'
+        self.write({
+            'active': (self.company_id.active_draft if self.company_id else
+                       self.env.user.company_id.active_draft),
+            'state': 'draft',
+        })
 
     @api.multi
     def button_new_version(self):
@@ -108,7 +109,6 @@ class MrpBom(models.Model):
 
     @api.multi
     def button_activate(self):
-        self.ensure_one()
         self.write({
             'active': True,
             'state': 'active'
@@ -116,7 +116,6 @@ class MrpBom(models.Model):
 
     @api.multi
     def button_historical(self):
-        self.ensure_one()
         self.write({
             'active': False,
             'state': 'historical',