Add new run_jobs_synchronously! helper for tests

Previously if you wanted to have jobs execute in test mode, you'd have
to do `SiteSetting.queue_jobs = false`, because the opposite of queue
is to execute.

I found this very confusing, so I created a test helper called
`run_jobs_synchronously!` which is much more clear about what it does.

spec/support/helpers.rb

@@ -5,6 +5,12 @@ module Helpers
     @next_seq = (@next_seq || 0) + 1
   end
 
+  # If you don't `queue_jobs` it means you want to run them synchronously. This method
+  # makes that more clear in tests. It is automatically reset after every test.
+  def run_jobs_synchronously!
+    SiteSetting.queue_jobs = false
+  end
+
   def log_in(fabricator = nil)
     user = Fabricate(fabricator || :user)
     log_in_user(user)