event: dynamically manage server-side RPC domain events

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.

daemon/libvirtd.h

@@ -51,7 +51,8 @@ struct daemonClientPrivate {
     /* Hold while accessing any data except conn */
     virMutex lock;
 
-    int domainEventCallbackID[VIR_DOMAIN_EVENT_ID_LAST];
+    daemonClientEventCallbackPtr *domainEventCallbacks;
+    size_t ndomainEventCallbacks;
     daemonClientEventCallbackPtr *networkEventCallbacks;
     size_t nnetworkEventCallbacks;