Wrap sending imsg to the RDE in a function and make sure that the ibuf

Wrap sending imsg to the RDE in a function and make sure that the ibuf
to the RDE is valid. The SE is stopping all sessions on exit and so
session_stop() is called which will send an imsg to the RDE which is no
longer there. Instead of fixing just one call fix all. Now the SE should
no longer crash when the RDE crashes.
OK sthen@