As noted in MDEV-11947, we should disable the InnoDB doublewrite buffer
during the tests, because when rewriting page checksums, innochecksum
would skip the pages that are in the doublewrite buffer area. Because
the doublewrite buffer is emptied on server startup and not shutdown,
we should initially start with the doublewrite buffer disabled, so that
there will be no warning messages for wrong page checksums in the
doublewrite buffer.

Also, correct the obvious typo where restart_options should have been
$restart_parameters, so that InnoDB is actually verifying that the
checksums were rewritten.