Fix RPC promise capabilities resolving before disembargoed harder.
Fix RPC promise capabilities resolving before disembargoed harder.

In the case where a remote promise resolved to another remote promise, disembargoes were not being handled correctly.

Specifically, imagine that remote promise P1 resolves to another remote promise P2, and P2 in turn resolved to local capability C.

If P2 resolved to C _before_ P1 resolved to P2, then when P1 resolved to P2, P1 would effectively inherit P2's embargo, but this is not sufficient:

- P2 might have started its embargo much earlier, and more messages may have been sent to P1 in the meantime. A new embargo is needed to ensure those later messages are delivered before local delivery starts.
- P2 might not have had an embargo at all, if no calls had been addressed to P2 before in resolved. But if calls had been addressed to P1 before its resolution, then those calls require an embargo.

mologie/capnproto,mologie/capnproto,mologie/capnproto