When a device is already open O_EXCL by another process the
`zpool import` will correctly fail. However, the default failure
message isn't very helpful. It may in fact be harmful if you
take its advise and destroy your pool.
cannot import 'tank': pool is busy
Destroy and re-create the pool from
a backup source.
Improve the error message in the EBUSY case to simply print a
message indicating that the devices are current in use. The user
will need to manually identify which process has the device open
exclusively and why.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>