ZTS: Add zpool_import_status.ksh to Makefile.am
The zpool_import_status.ksh test case was not being run because
it was not included in the Makefile.am.
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #15655