Do not exit with error status in case of no directory change

Created by: blueyed

As stated in https://github.com/joelthelion/autojump/issues/167#issuecomment-11489846 the internals of autojump changed, so that it might now return with an error status, in case the current directory stays the same (but matches).

Just a minor annoyance, and I mainly wanted to get it out of the other ticket.

TEST CASE:

1. mkdir /tmp/foobarbaz
2. cd /tmp/foobarbaz
3. cd
4. j foobar
  => goes to /tmp/foobarbaz
5. j foobar
  => ERROR:
autojump: directory 'foobar' not found
Try `autojump --help` for more information.