AppFramework does not allow caching

[rullzer]

The avatar controller sets the etag to the crc32 of the avatar.
However if I then use that etag with curl like:

curl -D - https://server/index.php/avatar/rullzer/32 --header 'If-None-Match: "4146254073"'

I do not get an 304.

I think this is caused by https://github.com/owncloud/core/blob/master/lib/private/appframework/http.php#L124. Since it compares the set ETag with the provided ETag. But the provided ETag has quotes.

[BernhardPosselt]

Can't do this one, fix should be straight forward though. Can you take care of this?

[rullzer]

Yep will do :)