Kernel adapter now returns is_cache_device=1 and newly added
metadata_compatible=0 in case of metadata detected with
differing version (instead of is_cache_device = 0).
This allows zero-superblock command to recognize old
cache instance and clear it.
casadm --script --check-cache-device still returns 'Is cache'='no'
in this case, as this layer only cares about metadata in current
version to be able to detect dirty datas tatus.
Signed-off-by: Adam Rutkowski <adam.j.rutkowski@intel.com>