ZTS: Fix EBUSY volume destroy failures

ZTS: Fix EBUSY volume destroy failures

It's possible for an unrelated process, like blkid, to have the
volume open when 'zfs destroy' is run.  Switch the cleanup functions
to the destroy_dataset() helper which handles this case by retrying
the destroy when the dataset is busy.  This was done not only for
volumes but also for file systems for consistency.

Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7854