tools: fix check_guests_shutdown loop

The recent fix to libvirt-guests.sh.in works for what it intended to fix
(variable scope) but failed to adapt the loop in check_guests_shutdown
correctly. Due to that it currently might detect all guests as "Failed to
determine state of guest" by bad var content or just assumes they are shut
down by picking up an empty variable.

This commit fixes loop to use the passed value and the call in the loop
to actually use the variable assigned in the iterated.

Fixes: 7e476356 "tools: fix variable scope in in check_guests_shutdown"
Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1764668Reviewed-by: NDariusz Gadomski <dariusz.gadomski@canonical.com>
Signed-off-by: NChristian Ehrhardt <christian.ehrhardt@canonical.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>

tools/libvirt-guests.sh.in

@@ -336,8 +336,8 @@ check_guests_shutdown()
     guests_to_check=$2
 
     guests_shutting_down=
-    for guest in $guests; do
-        if ! guest_is_on "$uri" "$guests_to_check" >/dev/null 2>&1; then
+    for guest in $guests_to_check; do
+        if ! guest_is_on "$uri" "$guest" >/dev/null 2>&1; then
             eval_gettext "Failed to determine state of guest: \$guest. Not tracking it anymore."
             echo
             continue