Create revisions in V2 app update

Revisions will now work with `cf start` and `cf restart`

[finishes #165542128](https://www.pivotaltracker.com/story/show/165542128)

Co-authored-by: Tim Downey <[email protected]>
Co-authored-by: Seth Boyles <[email protected]>

Author: tcdowney

app/actions/v2/app_update.rb

@@ -115,7 +115,7 @@ def start_or_stop(app, request_attrs)
         if request_attrs.key?('state')
           case request_attrs['state']
           when ProcessModel::STARTED
-            AppStart.start_without_event(app, create_revision: false)
+            AppStart.start_without_event(app)
           when ProcessModel::STOPPED
             V2::AppStop.stop(app, StagingCancel.new(@stagers))
           end

spec/unit/actions/v2/app_update_spec.rb

@@ -132,15 +132,16 @@ module VCAP::CloudController
           app.update(droplet_guid: droplet.guid)
         end
 
-        it 'does not create a revision' do
+        it 'creates a revision' do
           app.update(revisions_enabled: true)
 
           request_attrs = {
             'state' => ProcessModel::STARTED,
           }
 
           app_update.update(app, process, request_attrs)
-          expect(app.reload.revisions.count).to eq(0)
+          expect(app.reload.revisions.count).to eq(1)
+          expect(app.latest_revision.droplet_guid).to eq(droplet.guid)
         end
       end