fix https://jira.oceanobservatories.org/tasks/browse/OOIION-987

- fix OOIION-987: now all EventSubscriber's created by the platform agent are registered with BaseService.add_endpoint . 

- also fix leaked process in test_platform_status_launch_instruments_first_2_3: just add a missing shutdown call so the sub-platform LJ01D gets terminated by the root platform MJ01C when issued the SHUTDOWN command. (recall that the termination of a platform agent per se does not have any effect on its children.)