verify that multipath doesn't try to assign new devices in-use user_friendly
aliases.

steps:
1. setup config file and remove existing bindings file
2. create scsi_debug devices
3. start multipathd to create devices and bindings file
4. look at path device ordering in multipathd output
5. stop multipathd and remove devices
6. blacklist the devices which were multipathed early in the config file
7. remove the bindings file
8. restart multipathd to create devices, where the later devices grab the
   earlier user_friendly_names
9. stop multipathd
10. remove blacklists from the config file and remove bindings file
11. restart multipathd
12. Verify that all devices are there, the previously existing devices
    still have the same alias, and all the devices match the bindings file
13. reconfigure multipathd
14. Verify that all devices are still there and still match.