Do not send empty text-delta for equal files in update reporter.

* subversion/libsvn_repos/reporter.c
  (delta_files): Always use svn_repos__compare_files() function to check 
   that file content is changed regardless of IGNORE_ANCESTRY flag. 
   IGNORE_ANCESTRY flag is already handled on caller side in update_entry() 
   function.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1442555 13f79535-47bb-0310-9956-ffa450edef68