error-report: fix g_date_time_format assertion

The 'g_get_real_time' returns the number of microseconds since January
1, 1970 UTC, but 'g_date_time_new_from_unix_utc' needs the number of
seconds, so it will cause the invalid time input:

(process:279642): GLib-CRITICAL (recursed) **: g_date_time_format: assertion 'datetime != NULL' failed

Call function 'g_date_time_new_now_utc' instead, it has the same result
as 'g_date_time_new_from_unix_utc(g_get_real_time() / G_USEC_PER_SEC)';

Fixes: 73dab89 ("error-report: replace deprecated g_get_current_time() with glib >= 2.62")
Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20220424105036.291370-1-haiyue.wang@intel.com>

util/error-report.c

@@ -173,7 +173,7 @@ static char *
 real_time_iso8601(void)
 {
 #if GLIB_CHECK_VERSION(2,62,0)
-    g_autoptr(GDateTime) dt = g_date_time_new_from_unix_utc(g_get_real_time());
+    g_autoptr(GDateTime) dt = g_date_time_new_now_utc();
     /* ignore deprecation warning, since GLIB_VERSION_MAX_ALLOWED is 2.56 */
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"