Enable security group extension in PLUMgrid plugin

Implements: blueprint plumgrid-neutron-security-groups
Change-Id: I30392adff5e3250a1c4f9f1f04fc7e0587007226
diff --git a/lib/neutron_plugins/plumgrid b/lib/neutron_plugins/plumgrid
index 178bca7..00e2c95 100644
--- a/lib/neutron_plugins/plumgrid
+++ b/lib/neutron_plugins/plumgrid
@@ -46,8 +46,8 @@
 }
 
 function has_neutron_plugin_security_group {
-    # False
-    return 1
+    # return 0 means enabled
+    return 0
 }
 
 function neutron_plugin_check_adv_test_requirements {