event-test.py: Sync list of storage lifecycle events

https://bugzilla.redhat.com/show_bug.cgi?id=1578337

Since libvirt 3.8.0 we have 6 events: defined, undefined,
started, stopped, created, deleted. However, the last two were
missing in a string list that translates libvirt events (int)
into human readable strings.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>

examples/event-test.py

@@ -605,6 +605,8 @@ def storageEventToString(event):
                             "Undefined",
                             "Started",
                             "Stopped",
+                            "Created",
+                            "Deleted",
     )
     return storageEventStrings[event]