Try to create datadirectory to test whether the .htaccess works

Fixes https://github.com/owncloud/core/pull/11299#issuecomment-56968588 and also https://github.com/owncloud/core/issues/10628 together with https://github.com/owncloud/core/pull/11299#issuecomment-56968588 when backported.
Merge pull request #11324 from owncloud/tryToCreateDatadirectory

Try to create datadirectory to test whether the .htaccess works