rewrite logging in console (#788)

- enhance logging throughout the codebase
- all packages at pkg/ should never log
  or perform log.Fatal() instead packages
  should return errors through functions.
- simplified various user, group mapping
  and removed redundant functions.
- deprecate older flags like --tls-certificate
  --tls-key and --tls-ca as we do not use
  them anymore, keep them for backward compatibility
  for some time.

restapi/admin_arns.go

@@ -52,7 +52,7 @@ func getArns(ctx context.Context, client MinioAdmin) (*models.ArnsResponse, erro
 
 // getArnsResponse returns a list of active arns in the instance
 func getArnsResponse(session *models.Principal) (*models.ArnsResponse, *models.Error) {
-	mAdmin, err := newMAdminClient(session)
+	mAdmin, err := newAdminClient(session)
 	if err != nil {
 		return nil, prepareError(err)
 	}