ZTS: three small follow up fixes for #11167
Follow up fix for 0cb40fa3. Remove unused variables, don't source
unused libs and add missed cleanup.
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Attila Fülöp <attila@fueloep.org>
Closes #11311