spec: updated to match master
spec: updated to match master

- Updated SDK requirements
- Dropped EL6 support

Change-Id: I1a512ae3ce3690dbb6d87618b075f8c365078d2b
Signed-off-by: Sandro Bonazzola <fcb014d63786651910af5db2ecc5316c668188ef@redhat.com>

oVirt/ovirt-image-uploader,oVirt/ovirt-image-uploader,oVirt/ovirt-image-uploader