Removed force start from themes test

refs https://github.com/TryGhost/Toolbox/issues/135

- Looking closer into the reason why the test was failing without "forceStart" revealed that the server only start  was overoptimized - "initServicesForFrontend" should be a part of a backend as those are generic theme services.

core/boot.js

@@ -368,9 +368,9 @@ async function bootGhost({backend = true, frontend = true} = {}) {
         // Step 4 - Load Ghost with all its services
         debug('Begin: Load Ghost Services & Apps');
         await initCore({ghostServer, config, bootLogger, frontend});
+        await initServicesForFrontend();
 
         if (frontend) {
-            await initServicesForFrontend();
             await initFrontend();
         }
         const ghostApp = await initExpressApps({frontend, backend});

test/e2e-api/admin/themes.test.js

@@ -29,10 +29,7 @@ describe('Themes API', function () {
         // NOTE: this flag should not be here! the URL service re-initialization should be fixed instead
         //       The reason why this init doesn't work without "forceStart" is because during the "restartModeGhostStart"
         //       the routing.routerManager is never called with "start". That's why a full boot is needed
-        await localUtils.startGhost({
-            forceStart: true,
-            frontend: true
-        });
+        await localUtils.startGhost();
         ownerRequest = supertest.agent(config.get('url'));
         await localUtils.doAuth(ownerRequest);
     });