Fix pool_names_001_pos test case
After volume creation wait until the new block devices have settled
before destroying them. Failure to do some can result in EBUSY
being returned and the test case failing.
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #5636
Closes #5637