Reduce HashedWheelTimer instance number

Reading code and finding that we use HashedWheelTimer in OwnershipCache Class, from netty HashedWheelTimer java doc we know:

Do not create many instances.
HashedWheelTimer creates a new thread whenever it is instantiated and started. Therefore, you should make sure to create only one instance and share it across your application

then i grep the code base and found there're several HashedWheelTimer instantces be created seems. i think the current code could be improved (to reduce the thread num at least?)