On the log-message-templates branch, reinstate a check that prevents
us from setting a log message template more than once. This check was
accidentally removed in r1622710.

* subversion/libsvn_client/commit_util.c
  (svn_client_get_log_message_templates): If we already have a log messsage
   template from the defining_repos_relpath in question, don't allocate and
   set the template again.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/log-message-templates@1622711 13f79535-47bb-0310-9956-ffa450edef68