Add onServerAddOnStart and onServerAddOnStop plugin hooks
Add onServerAddOnStart and onServerAddOnStop plugin hooks

Reviewed By: mweststrate

Differential Revision: D34378231

fbshipit-source-id: e086eebcf94c01da76bfe8b88c6528bd21d89968

facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper,facebook/flipper