On the log-message-templates branch: Don't fetch log message templates
when we are not going to use them, to avoid doing unneeded (potentially
expensive) work.

This handles cases like
$ svn ci -m "My message"

* subversion/svn/util.c
  (svn_cl__get_log_message): Only create a default message if we are actually
    going to use it. Remove unnecessary initialization.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/log-message-templates@1624238 13f79535-47bb-0310-9956-ffa450edef68