Make PutObject a nop for an object which ends with "/" and size is '0' (#3603)

This helps majority of S3 compatible applications while not returning
an error upon directory create request.

Fixes #2965

cmd/object-handlers.go

@@ -409,7 +409,7 @@ func (api objectAPIHandlers) PutObjectHandler(w http.ResponseWriter, r *http.Req
 			return
 		}
 	}
-	if size == -1 && !contains(r.TransferEncoding, "chunked") {
+	if size == -1 {
 		writeErrorResponse(w, ErrMissingContentLength, r.URL)
 		return
 	}