remove config manager stop restriction (#340)

Author: andrewleap-optimizely

lib/optimizely/config_manager/http_project_config_manager.rb

@@ -102,11 +102,6 @@ def ready?
     end
 
     def start!
-      if @stopped
-        @logger.log(Logger::WARN, 'Not starting. Already stopped.')
-        return
-      end
-
       @async_scheduler.start!
       @stopped = false
     end