Client does not receive RPC after picking up a weapon attachement

[ernopp]

Repo:

1. Set up a scenario in which you have a player character who has weapon as a child.
2. Attach a weapon attachment to the weapon by setting the attachment actors parent to be the weapon on the server.
3. In the same bit of logic, send a ClientRPC from the attachment actor.

Result: The client does not receive the RPC.

If the RPC is multicast the issue will not occur.

Perhaps the simplest case of this is simply setting an actors parent and sending a ClientRPC on the actor on the same frame.

Internal Ticket

https://improbableio.atlassian.net/browse/UNR-2454