Honor connection pooling while tracing (#7979)

This PR fixes relying on r.Context().Done()
by setting

```
Connection: "close"
```

HTTP Header, this has detrimental issues for
client side connection pooling. Since this
header explicitly tells clients to turn-off
connection pooling. This causing pro-active
connections to be closed leaving many conn's
in TIME_WAIT state. This can be observed with
`mc admin trace -a` when running distributed
setup.

This PR also fixes tracing filtering issue
when bucket names have `minio` as prefixes,
trace was erroneously ignoring them.

cmd/handler-utils.go

@@ -394,20 +394,3 @@ func getHostName(r *http.Request) (hostName string) {
 	}
 	return
 }
-
-func isHTTPStatusOK(statusCode int) bool {
-	// List of success status.
-	var successStatus = []int{
-		http.StatusOK,
-		http.StatusCreated,
-		http.StatusAccepted,
-		http.StatusNoContent,
-		http.StatusPartialContent,
-	}
-	for _, okstatus := range successStatus {
-		if statusCode == okstatus {
-			return true
-		}
-	}
-	return false
-}