Locking on cache keys needs to check if the lock was actually aquired

In com.atlassian.confluence.cache.tangosol.hibernate.CoherenceHibernateCache.lock(Object) we don't check if the lock could actually be aquired. Instead we should provide a timeout argument to com.tangosol.util.ConcurrentMap.lock(Object, long) and check if the lock could be aquired within the given timeout. If the lock couldn't be aquired we need to throw an exception.