add gocritic/ruleguard checks back again, cleanup code. (#13665)

- remove some duplicated code
- reported a bug, separately fixed in #13664
- using strings.ReplaceAll() when needed
- using filepath.ToSlash() use when needed
- remove all non-Go style comments from the codebase

Co-authored-by: Aditya Manthramurthy <donatello@users.noreply.github.com>

cmd/erasure-object.go

@@ -46,7 +46,7 @@ import (
 // list all errors which can be ignored in object operations.
 var objectOpIgnoredErrs = append(baseIgnoredErrs, errDiskAccessDenied, errUnformattedDisk)
 
-/// Object Operations
+// Object Operations
 
 func countOnlineDisks(onlineDisks []StorageAPI) (online int) {
 	for _, onlineDisk := range onlineDisks {