Fix missing push diagnostics
Fix missing push diagnostics

Summary: It was possible for the recheck bookends to be sent without an accompanying message afterwards reporting *all* diagnostics. This would cause Nuclide to clear out diagnostics. This links them inextricably, so that if the recheck bookends are sent, they must be followed by a message with the complete set of diagnostics.

Reviewed By: avikchaudhuri

Differential Revision: D5348023

fbshipit-source-id: 9b3d1ce8a5e4131fef21e1826bd38177951956df

samwgoldman/flow,AgentME/flow,nmote/flow,jamesgpearce/flow,ylu1317/flow,gabelevi/flow,samwgoldman/flow,popham/flow,samwgoldman/flow,popham/flow,gabelevi/flow,jamesgpearce/flow,facebook/flow,TiddoLangerak/flow,gabelevi/flow,jamesgpearce/flow,MichaelDeBoey/flow,jamesgpearce/flow,facebook/flow,AgentME/flow,claudiopro/flow,gabelevi/flow,claudiopro/flow,mroch/flow,samwgoldman/flow,MichaelDeBoey/flow,TiddoLangerak/flow,claudiopro/flow,nmote/flow,MichaelDeBoey/flow,JonathanUsername/flow,facebook/flow,claudiopro/flow,JonathanUsername/flow,nmote/flow,JonathanUsername/flow,popham/flow,mroch/flow,JonathanUsername/flow,JonathanUsername/flow,TiddoLangerak/flow,ylu1317/flow,MichaelDeBoey/flow,popham/flow,mroch/flow,mroch/flow,samwgoldman/flow,AgentME/flow,ylu1317/flow,AgentME/flow,samwgoldman/flow,samwgoldman/flow,facebook/flow,JonathanUsername/flow,gabelevi/flow,nmote/flow,ylu1317/flow,jamesgpearce/flow,nmote/flow,gabelevi/flow,nmote/flow,jamesgpearce/flow,popham/flow,facebook/flow,mroch/flow,TiddoLangerak/flow,TiddoLangerak/flow,popham/flow,gabelevi/flow,mroch/flow,claudiopro/flow,facebook/flow,nmote/flow,ylu1317/flow,JonathanUsername/flow,facebook/flow,mroch/flow,jamesgpearce/flow,AgentME/flow,MichaelDeBoey/flow,popham/flow