Fix incomplete merge

Commit 66bd7445 changed the semantics of _JobProcessor on finished
jobs, and updated the related unittests in the 2.4 branch. It was then
merged to master, however on master there was an additional test for
this case, which was not updated.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>