Make compatible with django 1.8
diff --git a/xos/services/openvpn/admin.py b/xos/services/openvpn/admin.py
index 28e778d..b125c7b 100644
--- a/xos/services/openvpn/admin.py
+++ b/xos/services/openvpn/admin.py
@@ -64,6 +64,7 @@
 
     class Meta:
         model = OpenVPNService
+        fields = '__all__'
 
 
 class OpenVPNServiceAdmin(ReadOnlyAwareAdmin):
@@ -198,6 +199,7 @@
 
     class Meta:
         model = OpenVPNTenant
+        fields = '__all__'
 
 
 class OpenVPNTenantAdmin(ReadOnlyAwareAdmin):