FIX: correct urls for external urls

frontend/src/components/Navbar.vue

@@ -22,12 +22,13 @@
         <b-nav-item v-if="$sysinfo_mods_by_name['dhcp_leases']" to="/dhcp-leases/"
                     :active="$route.path.startsWith('/dhcp-leases/')">DHCP-Leases
         </b-nav-item>
-        <b-nav-item href="https://www-net.scc.kit.edu/~netadmin/natvs/user/wrapper.cgi/" target="_blank">
-          NATVS+
-        </b-nav-item>
-        <b-nav-item href="https://www-net.scc.kit.edu/~netadmin/netdoc/user/wrapper.cgi/" target="_blank">
+        <b-nav-item v-if="$sysinfo_js_mods.includes('usr_netdoc')" to="/usr_netdoc/"
+                    :active="$route.path.startsWith('/usr_netdoc/')">
           NETDOC
         </b-nav-item>
+        <b-nav-item :href="$sysinfo.host_oper_mode.is_prod?'https://www-net.scc.kit.edu/~netadmin/natvs/user/wrapper.cgi/':`https://www-net-${$sysinfo.host_oper_mode.mode}.scc.kit.edu/~netadmin/natvs/user/wrapper.cgi/`" target="_blank">
+          NATVS+
+        </b-nav-item>
       </b-navbar-nav>
       <b-navbar-nav class="ml-auto">
         <GlobalSearch/>