Fix format string warnings

A few more non-literal format strings in error log messages have crept
in. Fix them in the standard way - turn the format string into "%s"
with the original string as the arg.

src/qemu/qemu_conf.c

@@ -3033,7 +3033,7 @@ qemuBuildVirtioSerialPortDevStr(virDomainChrDefPtr dev)
             VIR_DOMAIN_DEVICE_ADDRESS_TYPE_VIRTIO_SERIAL)
         {
             qemuReportError(VIR_ERR_INTERNAL_ERROR,
-                            _("virtio serial device has invalid address type"));
+                            "%s", _("virtio serial device has invalid address type"));
             goto error;
         }
 

src/xen/xend_internal.c

@@ -5848,7 +5848,7 @@ xenDaemonFormatSxpr(virConnectPtr conn,
     if (def->clock.offset == VIR_DOMAIN_CLOCK_OFFSET_LOCALTIME) {
         if (def->clock.data.timezone) {
             virXendError(conn, VIR_ERR_CONFIG_UNSUPPORTED,
-                         _("configurable timezones are not supported"));
+                         "%s", _("configurable timezones are not supported"));
             goto error;
         }
 

src/xen/xm_internal.c

@@ -2330,7 +2330,7 @@ virConfPtr xenXMDomainConfigFormat(virConnectPtr conn,
         if (def->clock.offset == VIR_DOMAIN_CLOCK_OFFSET_LOCALTIME) {
             if (def->clock.data.timezone) {
                 xenXMError(conn, VIR_ERR_CONFIG_UNSUPPORTED,
-                           _("configurable timezones are not supported"));
+                           "%s", _("configurable timezones are not supported"));
                 goto cleanup;
             }