configuration-backups: take inventory value

geant/gap_ansible/roles/bc_templates/routers/nokia/general.j2

@@ -39,7 +39,7 @@
             </md-cli>
         </cli>
         <configuration-save>
-            <configuration-backups>5</configuration-backups>
+            <configuration-backups>{{ inv_config_backups | default(50) }}</configuration-backups>
             <incremental-saves>false</incremental-saves>
         </configuration-save>
         <netconf>