### Please describe the problem.

"git-annex enableremote box.com" fails with "git-annex: WebDAV test failed".  The server returns error message "The resource you tried to create already exists" (see below).

### What steps will reproduce the problem?

1. I initialize box.com special remote in desktop.  The path at box.com is at "gas/annex".

2. I enable the box.com special remote in laptop.  I got the error I described above.

### What version of git-annex are you using? On what operating system?

    $ git annex version  
    git-annex version: 5.20140831-g62e6ad8
    build flags: Assistant Webapp Webapp-secure Pairing Testsuite S3 WebDAV Inotify DBus DesktopNotify XMPP DNS Feeds Quvi TDFA CryptoHash
    key/value backends: SHA256E SHA1E SHA512E SHA224E SHA384E SKEIN256E SKEIN512E SHA256 SHA1 SHA512 SHA224 SHA384 SKEIN256 SKEIN512 WORM URL
    remote types: git gcrypt S3 bup directory rsync web webdav tahoe glacier ddar hook external
    $ uname -a
    Linux tkf-acer 3.12.9-2-ARCH #1 SMP PREEMPT Fri Jan 31 10:22:54 CET 2014 x86_64 GNU/Linux


### Please provide any additional information below.

I ran the following while with appropriate environment variable WEBDAV_USERNAM and WEBDAV_PASSWORD.

    me@desktop$ git-annex initremote box type=webdav url=https://dav.box.com/dav/gas/annex chunk=50mb encryption=shared
    
    me@laptop$ git-annex enableremote box.com
    enableremote box.com (testing WebDAV server...)
    
    git-annex: WebDAV test failed: StatusCodeException (Status {statusCode = 405, statusMessage = "Method Not Allowed"}) [("Server","nginx"),("Date","Sat, 27 Sep 2014 09:36:42 GMT"),("Content-Type","application/xml; charset=utf-8"),("Content-Length","247"),("Connection","keep-alive"),("Vary","Host"),("Allow","OPTIONS, GET, HEAD, DELETE, PROPFIND, PUT, PROPPATCH, COPY, MOVE, REPORT, LOCK, UNLOCK"),("X-Response-Body-Start","<?xml version=\"1.0\" encoding=\"utf-8\"?>\n<d:error xmlns:d=\"DAV:\" xmlns:s=\"http://sabredav.org/ns\">\n  <s:exception>Sabre_DAV_Exception_MethodNotAllowed</s:exception>\n  <s:message>The resource you tried to create already exists</s:message>\n</d:error>\n")] (CJ {expose = []}): user error
    failed
    git-annex: enableremote: 1 failed

> You are using an old version of git-annex; this bug was fixed in
> version 5.20140919. [[done]] --[[Joey]]
