Make requestype for Service sub category mandatory

git-svn-id: http://svn.code.sf.net/p/itop/code/trunk@2292 a333f486-631f-4898-b8df-5754b55c2be0

datamodels/2.x/itop-service-mgmt/datamodel.itop-service-mgmt.xml

@@ -1017,7 +1017,7 @@
           </values>
           <sql>request_type</sql>
           <default_value>incident</default_value>
-          <is_null_allowed>true</is_null_allowed>
+          <is_null_allowed>false</is_null_allowed>
           <display_style>radio_horizontal</display_style>
         </field>
         <field id="status" xsi:type="AttributeEnum">