Refactor code a bit to avoid "goto print_error" pattern.

* subversion/svn/notify.c
  (notify_body): New function, extracted from notify() with standard error 
   handling semantic.
  (notify): Call notify_body() and then handle errors during writing output
   if any.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1603419 13f79535-47bb-0310-9956-ffa450edef68