further improvements to newXLStorage (#14166)

- create internal erasure volumes only if the disk is unformatted
- return a copy of format data in xlStorage.ReadAll
- parse env vars only once, to be re-used by xl-storage

cmd/globals.go

@@ -341,6 +341,10 @@ var (
 	// List of local drives to this node, this is only set during server startup.
 	globalLocalDrives []StorageAPI
 
+	// Is MINIO_CI_CD set?
+	globalIsCICD bool
+
+	globalRootDiskThreshold uint64
 	// Add new variable global values here.
 )