Make symlink  of librbd to qemu's folder so it can detect it.

Per issue #7293.

Signed-off-by: Sandon Van Ness <sandon@inktank.com>
Merge pull request #1370 from ceph/wip-7293

Make symlink  of librbd to qemu's folder so it can detect it.

Reviewed-by: Josh Durgin <josh.durgin@inktank.com>