[FIX] hr_holidays: poorly designed demo data

If an user (or a developer) wants to install this module twice, she
could not before this patch. Because those demo data call a function
that crashes if the state of the demo data has been modified... and
modifies it!
We avoid this issue by resetting the states of the demo data
explicitely (before a deeper refactoring)

addons/hr_holidays/data/hr_holidays_demo.xml

@@ -8,6 +8,7 @@
         <field name="type">add</field>
         <field name="number_of_days_temp">20</field>
         <field name="employee_id" ref="hr.employee_root"/>
+        <field name="state">confirm</field>
     </record>
 
     <record id="hr_holidays_employee1_int_tour" model="hr.holidays">
@@ -18,6 +19,7 @@
         <field name="type">add</field>
         <field name="number_of_days_temp">7</field>
         <field name="employee_id" ref="hr.employee_root"/>
+        <field name="state">confirm</field>
     </record>
 
     <record id="hr_holidays_employee1_vc" model="hr.holidays">
@@ -51,6 +53,7 @@
         <field name="type">remove</field>
         <field name="number_of_days_temp">3</field>
         <field name="employee_id" ref="hr.employee_root"/>
+        <field name="state">confirm</field>
     </record>
 
     <!-- approve the leave request -->