BUG: update_event may change event time information

[wbi-ocd]

If event has a timezone specified, using update_event will shift event time of - TZ offset.

TEST

Create an event in tl with an tz offset update title using API -> time will be different

Fix

I'm not sure if this should be fixed in iris client on iris web.

IF fixed on iris clients:

replace

            "event_date": date_time.strftime('%Y-%m-%dT%H:%M:%S.%f') if date_time else event.get('event_date'),
            "event_tags": ','.join(tags) if tags else event.get('event_tags'),
            "event_tz": timezone_string if timezone_string else event.get('event_tz'),

by

            "event_date": date_time.strftime('%Y-%m-%dT%H:%M:%S.%f') if date_time else event.get('event_date_wtz'),
            "event_tags": ','.join(tags) if tags else event.get('event_tags'),
            "event_tz": timezone_string if timezone_string else event.get('event_tz'),

but it's a not really intuitive as it breaks the 1 to 1 mapping between retrieved event and updated object