Configure libvirt log filters from the command-line, at run time.

Install the package:

    $> dnf install libvirt-admin -y

Configure a libvirt log file:

    $> virt-admin daemon-log-outputs "1:file:/var/log/libvirt/libvirtd.log"

Configure the most useful logs (the following also allows to see the
communication between libvirt and QEMU -- e.g. QMP commands libvirt
sends to QEMU.  Especially, useful to debug all bugs relating to libvirt
and QEMU interactions):

    $> virt-admin daemon-log-filters \
        "1:libvirt 1:qemu 1:conf 1:security 3:event 3:json 3:file 3:object 1:util"

That's it; no need to restart the libvirt daemon.  The
`/var/log/libvirt/libvirtd.log` should now have the debug logs.

To turn off the dynamic log filters:

    $> virt-admin daemon-log-filters ""

    Check that the filters are actually removed, by running `virt-admin
    daemon-log-filters` (with no extra args), which should show an empty
    list.