[IMP] mail: do not follow activities by default

Activities are quite personal and linked to daily jobs of people using it.
Being notified of all activities is therefore not considered as default
behavior and should be a choice done by users. Subtype linked to logged
activities is now not followed by default anymore. It is still configurable
through subscription widget or parent subscription (project/task for example).

This commit is linked to task ID 1824141.

addons/crm/tests/test_crm_activity.py

@@ -59,7 +59,7 @@ class TestCrmMailActivity(TestCrmCases):
         self.assertFalse(internal_subtypes)
 
         # Add sale manager as follower of default subtypes
-        self.lead.message_subscribe([self.crm_salemanager.partner_id.id])
+        self.lead.message_subscribe([self.crm_salemanager.partner_id.id], subtype_ids=[self.env.ref('mail.mt_activities').id, self.env.ref('mail.mt_comment').id])
 
         activity = self.env['mail.activity'].sudo(self.crm_salesman.id).create({
             'activity_type_id': self.activity1.id,

addons/mail/data/mail_data.xml

@@ -57,7 +57,7 @@
         </record>
         <record id="mt_activities" model="mail.message.subtype">
             <field name="name">Activities</field>
-            <field name="default" eval="True"/>
+            <field name="default" eval="False"/>
             <field name="internal" eval="True"/>
             <field name="sequence" eval="90"/>
         </record>