Optimize locking behaviour in non-transactional caches

Situation: REPL_SYNC cache, non transactional, locking isolation level NONE
Problem: when multiple threads trying to write same key on multiple nodes, the operation ends up mostly in locking timeouts

Mircea mentioned that the locking behaviour for non-tx caches could be optimized as well as for tx-caches or use the same mechanisms.
(One single lock, independed number of owners)