Refactor config and split them in packages (#8351)

This change is related to larger config migration PR
change, this is a first stage change to move our
configs to `cmd/config/` - divided into its subsystems

cmd/storage-rest-server.go

@@ -29,6 +29,7 @@ import (
 	"time"
 
 	"github.com/gorilla/mux"
+	"github.com/minio/minio/cmd/config"
 	xhttp "github.com/minio/minio/cmd/http"
 	"github.com/minio/minio/cmd/logger"
 )
@@ -573,7 +574,8 @@ func registerStorageRESTHandlers(router *mux.Router, endpoints EndpointList) {
 		}
 		storage, err := newPosix(endpoint.Path)
 		if err != nil {
-			logger.Fatal(uiErrUnableToWriteInBackend(err), "Unable to initialize posix backend")
+			logger.Fatal(config.ErrUnableToWriteInBackend(err),
+				"Unable to initialize posix backend")
 		}
 
 		server := &storageRESTServer{storage, mustGetUUID()}