Make management API asynchronous

NOTE: This patch only changes API that pretends to be asynchronous.
Most of management operations are still performed synchronously.
The real asynchronism will be introduced in the next patches.

Signed-off-by: Robert Baldyga <robert.baldyga@intel.com>

src/ocf_core_priv.h

@@ -54,8 +54,6 @@ struct ocf_core {
 
 bool ocf_core_is_valid(ocf_cache_t cache, ocf_core_id_t id);
 
-int ocf_core_set_user_metadata_raw(ocf_core_t core, void *data, size_t size);
-
 int ocf_core_volume_type_init(ocf_ctx_t ctx);
 
 void ocf_core_volume_type_deinit(ocf_ctx_t ctx);