Fix the btcctl uptime command

commit 0b2998b
Author: cec489 <173723251+cec489@users.noreply.github.com>
Date:   Mon Jun 24 20:01:13 2024 +0000

    A cleaner fix is to set the startTime in the server Start() function
    which is where the server is actually started.

commit ae6c125
Author: cec489 <173723251+cec489@users.noreply.github.com>
Date:   Mon Jun 24 19:15:23 2024 +0000

    Fix the btcctl uptime command by moving the setting of startupTime

server.go

@@ -2483,6 +2483,7 @@ func (s *server) Start() {
 		// the RPC server are rebroadcast until being included in a block.
 		go s.rebroadcastHandler()
 
+		s.rpcServer.cfg.StartupTime = s.startupTime
 		s.rpcServer.Start()
 	}