Added killswitch for collection sync functionality

refs https://github.com/TryGhost/Arch/issues/80
refs 3960bfac1d

- The killswitch (a setting in host settings) is needed to control the feature on a hosted environment, so we can safely turn it off if it causes any major issues.

ghost/core/core/server/services/collections/service.js

@@ -31,6 +31,13 @@ class CollectionsServiceWrapper {
     }
 
     async init() {
+        const config = require('../../../shared/config');
+        const labs = require('../../../shared/labs');
+        // host setting OR labs "collections" flag has to be enabled to run collections service
+        if (!config.get('hostSettings:collections:enabled') && !(labs.isSet('collections'))) {
+            return;
+        }
+
         if (inited) {
             return;
         }

ghost/core/test/e2e-api/admin/posts-bulk.test.js

@@ -8,6 +8,7 @@ describe('Posts Bulk API', function () {
 
     before(async function () {
         mockManager.mockLabsEnabled('collections');
+
         agent = await agentProvider.getAdminAPIAgent();
 
         // Note that we generate lots of fixtures here to test the bulk deletion correctly