Log the libvirt error when state changes fail

[jelly]

For example for RHEL-10-1 in CI turning a machine off sometimes errors out without any details.

---

Issue is probably a random hard triggered:

Jun 02 03:29:28 rhel-10-1-127-0-0-2-2201 setroubleshoot[50308]: SELinux is preventing /usr/bin/swtpm from read access on the file /tmp/.swtpm_setup.pidfile.10HG72. For complete SELinux messages run: sealert -l ee0e4922-4767-4308-bbe3-6001dc7a887a
Jun 02 03:29:28 rhel-10-1-127-0-0-2-2201 setroubleshoot[50308]: SELinux is preventing /usr/bin/swtpm from read access on the file /tmp/.swtpm_setup.pidfile.10HG72.
                                                                
                                                                *****  Plugin catchall (100. confidence) suggests   **************************
                                                                
                                                                If you believe that swtpm should be allowed read access on the .swtpm_setup.pidfile.10HG72 file by default.
                                                                Then you should report this as a bug.
                                                                You can generate a local policy module to allow this access.
                                                                Do
                                                                allow this access for now by executing:
                                                                # ausearch -c 'swtpm' --raw | audit2allow -M my-swtpm
                                                                # semodule -X 300 -i my-swtpm.pp

[jelly]

And now you don't flake ;-)

Should flake 40% https://cockpit-logs.us-east-1.linodeobjects.com/pull-2166-95ff5caa-20250602-031619-rhel-10-1/log.html

Let's apply a bigger hammer...

[mvollmer]

@jelly, are you still working on this?