slapos_cloud: Show slave/not slave instead portal type

Reduce the size of columns

master/bt5/slapos_cloud/SkinTemplateItem/portal_skins/slapos_cloud/HostingSubscription_view.xml

@@ -96,6 +96,7 @@
                       <list>
                         <string>listbox_aggregate_parent_title</string>
                         <string>listbox_aggregate_default_ipv6</string>
+                        <string>listbox_is_slave</string>
                       </list>
                     </value>
                 </item>

master/bt5/slapos_cloud/SkinTemplateItem/portal_skins/slapos_cloud/HostingSubscription_view/listbox.xml

@@ -143,8 +143,8 @@
                           <string>IPv6</string>
                         </tuple>
                         <tuple>
-                          <string>portal_type</string>
-                          <string>Portal Type</string>
+                          <string>is_slave</string>
+                          <string>Slave</string>
                         </tuple>
                         <tuple>
                           <string>translated_validation_state_title</string>