Improve L1 consitency with backup owners

ISPN-3648 fixed an issue that can occur when a backup owner replies with an outdated value.

More details on the original issue can be found at ISPN-3426.

This JIRA is to improve this fix to be something more desirable.

There are a few ways that this could be done.

1. Change it so that remote gets only go to the primary owner, which guarantees consistency with that owner (this still has issues with fail over when that primary owner goes down). Also may have performance issues since we don't have backup owners to respond faster.
2. Change it so that values are only added to L1 if the value was retrieved from the primary owner. (note there is still some stuff to think about for fail over here)
3. Multicast the invalidation message from the primary owner after updating the value. This is the simplest approach (no requestors map required), but may also have some performance concerns.