[horde] WebDAV potocol version error not handled properly

[Tom Buehlmann]

Hello all!

I have two installations of H4 on different Servers.

I tried to aquire a WebDAV-Calendar from one H4 to another.
Shortly after the message "You have added the Calendar"
i got the Error: " This server uses an older version of the
WebDAV-Protocol".
Kronolith was unusable after with the same error shown.
I had to remove the rogue WebDAV-Calender URL  directly in the database.
The logs showed nothing suspicious.

Maybe a bug in the sync code or kronolith?

- Tom