[Attendees] Don't set RSVP=TRUE for own account

[rfc2822]

Should be taken into account when writing the new Attendee builder.

1. Create event in DAVx5 as organizer.
2. Own account is used for ORGANIZER and also added as ATTENDEE.
3. The Attendee has RSVP=TRUE.

However RSVP is not needed for the own account, because the user can select their status anyway.