qemu.tests.qmp_event_notification: Fix config main_monitor

The main monitor name is overriden to hmp1 and causes test failures...
Signed-off-by: NLukáš Doktor <ldoktor@redhat.com>

qemu/tests/cfg/qmp_event_notification.cfg

@@ -6,7 +6,7 @@
     check_timeout = 360
     monitors = ' hmp1 qmp1 qmp2'
     monitor_type_qmp1 = qmp
-    main_monitor = humanmonitor1
+    main_monitor = hmp1
     monitor_type = human
     monitor_type_qmp2 = qmp
     variants: