client Channel search bypass

Bypass the broadcast search phase and directly connect
to a specific server and issue CMD_CREATE_CHANNEL.

Note, due to pvAccessCPP buggyness, this can only be relied
upon to connect with the unadvertised magic 'server' PV.

src/clientmon.cpp

@@ -642,10 +642,11 @@ std::shared_ptr<Subscription> MonitorBuilder::exec()
     });
 
     auto name(std::move(_name));
-    context->tcp_loop.dispatch([op, context, name]() {
+    auto server(std::move(_server));
+    context->tcp_loop.dispatch([op, context, name, server]() {
         // on worker
 
-        op->chan = Channel::build(context, name);
+        op->chan = Channel::build(context, name, server);
 
         op->chan->pending.push_back(op);
         op->chan->createOperations();