Fix the protected branches factory.

1. Previously, we were using `after_create` to create access levels.

2. At the time of protected branch creation, there are _no_ access
   levels present, which is invalid, and creation fails.

3. Fixed by setting access levels before the protected branch is created.

spec/factories/protected_branches.rb

@@ -3,9 +3,9 @@ FactoryGirl.define do
     name
     project
 
-    after(:create) do |protected_branch|
-      protected_branch.push_access_levels.create!(access_level: Gitlab::Access::MASTER)
-      protected_branch.merge_access_levels.create!(access_level: Gitlab::Access::MASTER)
+    before(:create) do |protected_branch|
+      protected_branch.push_access_levels.new(access_level: Gitlab::Access::MASTER)
+      protected_branch.merge_access_levels.new(access_level: Gitlab::Access::MASTER)
     end
 
     trait :developers_can_push do