-delay serving requests until plugin is ready

git-svn-id: https://gnunet.org/svn/gnunet@34780 140774ce-b5e7-0310-ab8b-a85725594a96
-shutdown alone does not move to ready list

git-svn-id: https://gnunet.org/svn/gnunet@34781 140774ce-b5e7-0310-ab8b-a85725594a96
-use flag to check for readyness

git-svn-id: https://gnunet.org/svn/gnunet@34782 140774ce-b5e7-0310-ab8b-a85725594a96
-update priority to shutdown if that is being used

git-svn-id: https://gnunet.org/svn/gnunet@34783 140774ce-b5e7-0310-ab8b-a85725594a96