rest/storage: Remove racy LastError usage (#8817)

instead perform a liveness check call to
verify if server is online and print relevant
errors.

Also introduce a StorageErr string error type
instead of errors.New() deprecate usage of
VerifyFileError, DeleteFileError for gob,
change in datastructure also requires bump in
storage REST version to v13.

Fixes #8811

cmd/server-main.go

@@ -45,8 +45,7 @@ func init() {
 	globalConsoleSys = NewConsoleLogger(context.Background())
 	logger.AddTarget(globalConsoleSys)
 
-	gob.Register(VerifyFileError(""))
-	gob.Register(DeleteFileError(""))
+	gob.Register(StorageErr(""))
 }
 
 // ServerFlags - server command specific flags