Fix zpool_import_all_001_pos

Cleanup zpool_import_all_001_pos to no longer use devices.
The test is meant to test zpool import -a and by no longer
requiring devices, a number of dependencies are no longer
necessary.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Closes #6198