qemu: Enable disconnecting SPICE clients without changing password

Libvirt updates the configuration of SPICE server only when something
changes. This is unfortunate when the user wants to disconnect a
existing spice session when the connected attribute is already
"disconnect".

This patch modifies the conditions for calling the password updater to
be called when nothing changes, but the connected attribute is already
"disconnect".

src/qemu/qemu_hotplug.c

@@ -1539,7 +1539,7 @@ qemuDomainChangeGraphics(struct qemud_driver *driver,
                             _("cannot change listen address setting on spice graphics"));
             return -1;
         }
-        if (STRNEQ_NULLABLE(oldListenNetwork,newListenNetwork)) {
+        if (STRNEQ_NULLABLE(oldListenNetwork, newListenNetwork)) {
             qemuReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                             _("cannot change listen network setting on spice graphics"));
             return -1;
@@ -1551,11 +1551,16 @@ qemuDomainChangeGraphics(struct qemud_driver *driver,
             return -1;
         }
 
-        /* If a password lifetime was, or is set, then we must always run,
-         * even if new password matches old password */
+        /* We must reset the password if it has changed but also if:
+         * - password lifetime is or was set
+         * - the requested action has changed
+         * - the action is "disconnect"
+         */
         if (olddev->data.spice.auth.expires ||
             dev->data.spice.auth.expires ||
             olddev->data.spice.auth.connected != dev->data.spice.auth.connected ||
+            dev->data.spice.auth.connected ==
+            VIR_DOMAIN_GRAPHICS_AUTH_CONNECTED_DISCONNECT ||
             STRNEQ_NULLABLE(olddev->data.spice.auth.passwd,
                             dev->data.spice.auth.passwd)) {
             VIR_DEBUG("Updating password on SPICE server %p %p",