Enable qemu guest agent usage

[gboutry]

Set layout directive to allow usage of qemu guest agent on openstack-hypervisor

Example of working commands:

root@bm0:/home/ubuntu# virsh qemu-agent-command instance-00000007 '{"execute":"guest-ping"}'
{"return":{}}
virsh qemu-agent-command instance-00000007 '{"execute": "guest-info"}'
{"return":{"version":"6.2.0","supported_commands":[{"enabled":true,"name":"guest-ssh-remove-authorized-keys","success-response":true},{"enabled":true,"name":"guest-ssh-add-authorized-keys","success-response":true},{"enabled":true,"name":"guest-ssh-get-authorized-keys","success-response":true},{"enabled":false,"name":"guest-get-devices","success-response":true},{"enabled":true,"name":"guest-get-osinfo","success-response":true},{"enabled":true,"name":"guest-get-timezone","success-response":true},{"enabled":true,"name":"guest-get-users","success-response":true},{"enabled":true,"name":"guest-get-host-name","success-response":true},{"enabled":true,"name":"guest-exec","success-response":true},{"enabled":true,"name":"guest-exec-status","success-response":true},{"enabled":true,"name":"guest-get-memory-block-info","success-response":true},{"enabled":true,"name":"guest-set-memory-blocks","success-response":true},{"enabled":true,"name":"guest-get-memory-blocks","success-response":true},{"enabled":true,"name":"guest-set-user-password","success-response":true},{"enabled":true,"name":"guest-get-fsinfo","success-response":true},{"enabled":true,"name":"guest-get-disks","success-response":true},{"enabled":true,"name":"guest-set-vcpus","success-response":true},{"enabled":true,"name":"guest-get-vcpus","success-response":true},{"enabled":true,"name":"guest-network-get-interfaces","success-response":true},{"enabled":true,"name":"guest-suspend-hybrid","success-response":false},{"enabled":true,"name":"guest-suspend-ram","success-response":false},{"enabled":true,"name":"guest-suspend-disk","success-response":false},{"enabled":true,"name":"guest-fstrim","success-response":true},{"enabled":true,"name":"guest-fsfreeze-thaw","success-response":true},{"enabled":true,"name":"guest-fsfreeze-freeze-list","success-response":true},{"enabled":true,"name":"guest-fsfreeze-freeze","success-response":true},{"enabled":true,"name":"guest-fsfreeze-status","success-response":true},{"enabled":true,"name":"guest-file-flush","success-response":true},{"enabled":true,"name":"guest-file-seek","success-response":true},{"enabled":true,"name":"guest-file-write","success-response":true},{"enabled":true,"name":"guest-file-read","success-response":true},{"enabled":true,"name":"guest-file-close","success-response":true},{"enabled":true,"name":"guest-file-open","success-response":true},{"enabled":true,"name":"guest-shutdown","success-response":false},{"enabled":true,"name":"guest-info","success-response":true},{"enabled":true,"name":"guest-set-time","success-response":true},{"enabled":true,"name":"guest-get-time","success-response":true},{"enabled":true,"name":"guest-ping","success-response":true},{"enabled":true,"name":"guest-sync","success-response":true},{"enabled":true,"name":"guest-sync-delimited","success-response":true}]}}