emulators/qemu-guest-agent: not working at 24.1 -> 24.7 upgrade

[deimosian]

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• [x] I have read the contributing guide lines at https://github.com/opnsense/core/blob/master/CONTRIBUTING.md
• [x] I am convinced that my issue is new after having checked both open and closed issues at https://github.com/opnsense/core/issues?q=is%3Aissue

Describe the bug

QEMU Guest Agent does not work after 24.1 -> 24.7 upgrade.

To Reproduce

Steps to reproduce the behavior:

1. Run OPNsense 24.1 in QEMU environment, eg Proxmox, with QEMU Agent installed.
2. Update from 24.1.x to 24.7.x.
3. Check hypervisor for QEMU Agent connection.

Expected behavior

QEMU Agent should remain installed and communicate with the host.

Describe alternatives you considered

N/A. There are no practical alternatives to having the proper agent.

[fraenki]

The plugin needs to move to the qemu port and activate the "guestagent" flavor: https://github.com/freebsd/freebsd-ports/blob/main/emulators/qemu/Makefile https://www.freshports.org/emulators/qemu-guest-agent/

I'll take care of this.