m/c/metroctl: move common impl to m/c/m/core

This moves the implementation shared between CLI commands into metroctl
core package.

Change-Id: I93624a07356accf3441f02e6ecd8e91d5b71e66e
Reviewed-on: https://review.monogon.dev/c/monogon/+/843
Tested-by: Jenkins CI
Reviewed-by: Sergiusz Bazanski <serge@monogon.tech>
diff --git a/metropolis/cli/metroctl/main.go b/metropolis/cli/metroctl/main.go
index d616714..949eb63 100644
--- a/metropolis/cli/metroctl/main.go
+++ b/metropolis/cli/metroctl/main.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"log"
 	"path/filepath"
 
 	"github.com/adrg/xdg"
@@ -35,6 +36,14 @@
 	rootCmd.PersistentFlags().BoolVar(&flags.verbose, "verbose", false, "Log additional runtime information")
 }
 
+// rpcLogger passes through the cluster resolver logs, if "--verbose" flag was
+// used.
+func rpcLogger(f string, args ...interface{}) {
+	if flags.verbose {
+		log.Printf("resolver: " + f, args...)
+	}
+}
+
 func main() {
 	cobra.CheckErr(rootCmd.Execute())
 }