qemuDomainObjBeginJob: Don't account DESTROY job to maxQueuedJobs

qemuDomainObjBeginJob: Don't account DESTROY job to maxQueuedJobs

When trying to destroy a domain (e.g. because we've seen EOF on
the monitor) we try to acquire QEMU_JOB_DESTROY. However, if
max_queued is set in qemu.conf this may fail and since our code
doesn't count on that we will still report domain as active even
though the qemu process is long gone. More specifically, if we've
seen EOF on the monitor, qemuProcessHandleMonitorEOF() is called
which sends MONITOR_EOF job to the event worker pool and
unregisters monitor from the event loop. The worker pool calls
processMonitorEOFEvent() which tries to set job which may fail
due to the limit as described above.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>