fix: handle concurrent lockers with multiple optimizations (#10640)

- select lockers which are non-local and online to have
  affinity towards remote servers for lock contention

- optimize lock retry interval to avoid sending too many
  messages during lock contention, reduces average CPU
  usage as well

- if bucket is not set, when deleteObject fails make sure
  setPutObjHeaders() honors lifecycle only if bucket name
  is set.

- fix top locks to list out always the oldest lockers always,
  avoid getting bogged down into map's unordered nature.

cmd/object-api-utils.go

@@ -322,6 +322,10 @@ func isStringEqual(s1 string, s2 string) bool {
 
 // Ignores all reserved bucket names or invalid bucket names.
 func isReservedOrInvalidBucket(bucketEntry string, strict bool) bool {
+	if bucketEntry == "" {
+		return true
+	}
+
 	bucketEntry = strings.TrimSuffix(bucketEntry, SlashSeparator)
 	if strict {
 		if err := s3utils.CheckValidBucketNameStrict(bucketEntry); err != nil {