iotests: correct resultclass type in ReproducibleTestRunner

iotests: correct resultclass type in ReproducibleTestRunner

I have a vague memory that I suggested this base class to Vladimir and
said "Maybe someday it will break, and I'll just fix it then." Guess
that's today.

Fixes various mypy errors in the "make check-tox" python test for at
least Python3.8; seemingly requires a fairly modern mypy and/or Python
base version to trigger.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-ID: <20241101173700.965776-3-jsnow@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>