ZTS: Retry redundancy_draid_spare[1,3].ksh

The redundancy_draid_spare1.ksh and redundancy_draid_spare3.ksh test
cases are a little to strict for the sequential resilver case. While
unlikely it is possible that a handful of correctable checksum errors
will be reported resulting in a test failure. Update the zts-report.py
script to allow this the test case to be retried if requested.

Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #13318