[release-18.0] Bypass cobra completion commands so they still function (

#14217) (#14234)

Co-authored-by: vitess-bot[bot] <108069721+vitess-bot[bot]@users.noreply.github.com>

go/cmd/vtctldclient/command/root.go

@@ -141,6 +141,13 @@ func getClientForCommand(cmd *cobra.Command) (vtctldclient.VtctldClient, error)
 		}
 	}
 
+	// Reserved cobra commands for shell completion that we don't want to fail
+	// here.
+	switch {
+	case cmd.Name() == "__complete", cmd.Parent() != nil && cmd.Parent().Name() == "completion":
+		return nil, nil
+	}
+
 	if VtctldClientProtocol != "local" && server == "" {
 		return nil, errNoServer
 	}