jobs: fix verb references in docs

jobs: fix verb references in docs

These point to the job versions now, not the blockjob versions which
don't really exist anymore.

Except set-speed, which does. It sticks out like a sore thumb. This
patch doesn't fix that, but it doesn't make it any worse, either.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>