etcdctl: allow move-leader to connect to multiple endpoints with TLS

The mustClientForCmd function is responsible for parsing environment
variables and flags into configuration data. A change was made in etcd-io#9382 to call Fatal if a flag is provided multiple times.
This means that we cannot call the mustClientForCmd function more than
once, since it will think that flags parsed the first time are now being
redefined and error out.

etcdctl/ctlv3/command/move_leader_command.go

@@ -42,7 +42,8 @@ func transferLeadershipCommandFunc(cmd *cobra.Command, args []string) {
 		ExitWithError(ExitBadArgs, err)
 	}
 
-	c := mustClientFromCmd(cmd)
+	cfg := clientConfigFromCmd(cmd)
+	c := cfg.mustClient()
 	eps := c.Endpoints()
 	c.Close()
 
@@ -52,7 +53,6 @@ func transferLeadershipCommandFunc(cmd *cobra.Command, args []string) {
 	var leaderCli *clientv3.Client
 	var leaderID uint64
 	for _, ep := range eps {
-		cfg := clientConfigFromCmd(cmd)
 		cfg.endpoints = []string{ep}
 		cli := cfg.mustClient()
 		resp, serr := cli.Status(ctx, ep)