Don't start libjobqueue worker unless running under the Server

In particular, this avoids starting queue workers in the console which
leads to ActiveJob emitting log messages into the console, which is
confusing and distracting.

Author: mattbnz

lib/litestack/litejobqueue.rb

@@ -179,6 +179,7 @@ def schedule(spawn = false, &block)
 
   # create a worker according to environment
   def create_worker
+    return if defined?(Rails) && !defined?(Rails::Server)
     Litescheduler.spawn do
       worker_sleep_index = 0
       while @running