Zero metadata if on-disk version differs from current

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>

modules/include/cas_ioctl_codes.h

@@ -314,7 +314,12 @@ struct kcas_core_pool_remove {
 
 struct kcas_cache_check_device {
 	char path_name[MAX_STR_LEN]; /**< path to a device */
-	bool is_cache_device;
+	bool is_cache_device; /* OCF metadata detected */
+
+	/* following bool flags are defined is_cache_device == 1 */
+	bool metadata_compatible; /* OCF metadata is in current version */
+
+	/* following bool flags are defined iff is_metadata_compatible == 1 */
 	bool clean_shutdown;
 	bool cache_dirty;
 	bool format_atomic;