Introduces an API for encoding the header field for outgoing messages
allowing some duplicated code to be eliminated
* qemud/dispatch.c, qemud/dispatch.h: add remoteEncodeClientMessageHeader
for encoding message header. Update remoteDispatchClientRequest to
use this method.
* qemud/remote.c: Update remoteDispatchDomainEventSend to use the
generic remoteEncodeClientMessageHeader() for encoding event
message hedaders. Push some logic from remoteRelayDomainEvent
down into remoteDispatchDomainEventSend.
852fa7d04a