[FIX] tests: fix test retry mechanism for subtests

When a subtest fails, the failure or error is taken into account and even if
the subtest was silenced the test itself logs an ERROR with the count of
failures.

With this commit, at the first try, the subtest result is not taken into
account.

closes odoo/odoo#91974

X-original-commit: 96ca5bb6d7aeb54dfb8d5453edaf04b2ea903d41
Signed-off-by: Christophe Monniez (moc) <moc@odoo.com>