Improved ownCloud tests

Improved the ownCloud tests:

- The checks for remote.php/caldav and remote.php/carddav are unneeded as they are always provided together with the remote.php/webdav which is already checked

- Added a detection for an unprotected ownCloud data directory which contains the files of all users.
--> Maybe the check could be improved to as the data directory contains the following files:

``
-rw-r--r--  1 www-data www-data    268 Mai 18 14:05 .htaccess
-rw-r--r--  1 www-data www-data      0 Mai 18 14:05 index.html
-rw-r--r--  1 www-data www-data      0 Mai 18 14:05 .ocdata
-rw-r--r--  1 www-data www-data 104448 Jul  7 08:43 owncloud.db
-rw-r-----  1 www-data www-data   1256 Jul  7 08:41 owncloud.log
``

Problems here:

- The .htaccess file is probably not accessible on most webservers
- index.html and .ocdata are empty -> Can cause FPs when checking for "200" only
- owncloud.db is the SQLite database which is not widely used and doesn't exist on every system
- owncloud.log can be moved to another location and it could be possible that it is also empty

But i think the check for the owncloud.log should be the best check in this case.

Any other opinions?