The QMP block-job-resume command and cancellation may want to reset the
job's iostatus.  The next patches add a user who does not want to reset
iostatus so move it up to block_job_enter() callers.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1466096189-6477-2-git-send-email-stefanha@redhat.com