For issue #3913, make 'svnrdump load' interactive by default if none of
the --*-interactive options were given, and if no username and password
were provided on the command line.

Allows 'svnrdump load' authentication to work without requiring users to
type --force-interactive.

* subversion/svnrdump/svnrdump.c
  (main): Delay determination of non_interactive's value until information
   about the subcommand is available. Set force_interactive under the
   conditions described above.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1467587 13f79535-47bb-0310-9956-ffa450edef68