Avoid double-decrement of level->todo
Avoid double-decrement of level->todo

If a job's dispatch function deletes the job, we may end up decrementing
the job queue's todo count twice. Verify that the job is on the queue
before decrementing.

ClusterLabs/libqb,kgaillot/libqb,rubenk/libqb,rubenk/libqb,davidvossel/libqb,gao-yan/libqb,kgaillot/libqb,kgaillot/libqb,davidvossel/libqb,ClusterLabs/libqb,gao-yan/libqb,ClusterLabs/libqb