all: eliminate usage of global ProxyLogger

So setting up logging for ctrld binary and ctrld packages could be done
more easily, decouple the required setup for interactive vs daemon
running.

This is the first step toward replacing rs/zerolog libary with a
different logging library.

internal/clientinfo/merlin.go

@@ -15,6 +15,7 @@ const merlinNvramCustomClientListKey = "custom_clientlist"
 
 type merlinDiscover struct {
 	hostname sync.Map // mac => hostname
+	logger   *ctrld.Logger
 }
 
 func (m *merlinDiscover) refresh() error {
@@ -25,7 +26,7 @@ func (m *merlinDiscover) refresh() error {
 	if err != nil {
 		return err
 	}
-	ctrld.ProxyLogger.Load().Debug().Msg("reading Merlin custom client list")
+	m.logger.Debug().Msg("reading Merlin custom client list")
 	m.parseMerlinCustomClientList(out)
 	return nil
 }