ZTS: Fix auto_replace_001_pos test

The root cause of these failures is that udev can notify the
ZED of newly created partition before its links are created.
Handle this by allowing an auto-replace to briefly wait until
udev confirms the links exist.

Distill this test case down to its essentials so it can be run
reliably. What we need to check is that:

1. A new disk, in the same physical location, is automatically brought online when added to the system,
2. It completes the replacement process, and
3. The pool is now ONLINE and healthy.

There is no need to remove the scsi_debug module. After exporting
the pool the disk can be zeroed, removed, and then re-added to the
system as a new disk.

Reviewed by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #8051