kvm: set LIBVIRTD_ARGS so libvirtd listens on Debian and Ubuntu hosts

cloudstack-setup-agent sets up live migration on Debian and Ubuntu by
writing libvirtd_opts='-l' to /etc/default/libvirtd and masking the libvirtd
sockets. The libvirtd.service unit on current releases reads LIBVIRTD_ARGS
from that file instead (Debian 12 and 13 run "libvirtd $LIBVIRTD_ARGS" with
"--timeout 120" as the default), so after adding a host libvirtd runs
without --listen, nothing listens on the migration ports and live migration
fails with "unable to connect to server". Also set LIBVIRTD_ARGS="--listen",
and keep libvirtd_opts for older units that still read it.

Author: nagaboinaramgopal

python/lib/cloudutils/serviceConfig.py

@@ -722,6 +722,7 @@ def setupLiveMigration(self):
         elif os.path.exists("/etc/default/libvirtd"):
             cfo = configFileOps("/etc/default/libvirtd", self)
             cfo.replace_or_add_line("libvirtd_opts=","libvirtd_opts='-l'")
+            cfo.replace_or_add_line("LIBVIRTD_ARGS=","LIBVIRTD_ARGS=\"--listen\"")
             if os.path.exists("/lib/systemd/system/libvirtd.socket"):
                 bash("/bin/systemctl mask \
                     libvirtd.socket \