package/sconeserver: disable image

package/sconeserver: disable image

Build of http::sconesite::image module was silently broken until commit
d3b818c3cf0990117a8b59fcfc6c212f310ae6ec

However, sconeserver fails to build with ImageMagick because:
- it checks for ImageMagick++.pc instead of ImageMagick.pc
- it uses the transform function which has been removed from the public
  API since version 7.0.1-0 and
  https://github.com/ImageMagick/ImageMagick/commit/06f590165f0505d42005264893fe14a9e8a79986

As sconeserver does not seem to be maintained anymore, drop
BR2_PACKAGE_SCONESERVER_HTTP_SCONESITE_IMAGE.

Fixes:
 - http://autobuild.buildroot.org/results/895ab582d1140f7677fc1c6934fa2e0c47c49f20

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
[Arnout: add legacy symbol. It costs us exactly nothing, and if someone
actually had that selected, they know what's going on.]