Quoting the TAP specification: "The plan tells how many tests will be
run [...]. It’s a check that the test file hasn’t stopped prematurely."
That's a good idea of course, so let's support that in the iotest
testrunner, too.

Signed-off-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220223095816.2663005-1-thuth@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>