This patch continues the earlier conversion made for network
events, with a goal of introducing server-side event filtering
in a later patch.  Actual behavior is unchanged without
further RPC changes.

* daemon/libvirtd.h (daemonClientPrivate): Alter the tracking of
domain events.
* daemon/remote.c (remoteClientInitHook, remoteClientFreeFunc)
(remoteRelayDomainEvent*)
(remoteDispatchConnectDomainEventRegister)
(remoteDispatchConnectDomainEventRegisterAny): Track domain
callbacks dynamically.