martian: fix and simplify isCloseable

Notice that it used to return neterr.Timeout error as closable.
This was wrong as we want to retry on any timeout error.
This is why handle loop checks for maxConsecutiveErrors.

Author: Choraden

internal/martian/errors.go

@@ -82,18 +82,16 @@ func isClosedConnError(err error) bool {
 
 // isCloseable reports whether err is an error that indicates the client connection should be closed.
 func isCloseable(err error) bool {
-	if errors.Is(err, io.EOF) ||
-		errors.Is(err, io.ErrUnexpectedEOF) ||
-		errors.Is(err, io.ErrClosedPipe) {
-		return true
+	if err == nil {
+		return false
 	}
 
 	var neterr net.Error
-	if ok := errors.As(err, &neterr); ok && neterr.Timeout() {
-		return true
-	}
-
-	return strings.Contains(err.Error(), "tls:")
+	return errors.Is(err, io.EOF) ||
+		errors.Is(err, io.ErrUnexpectedEOF) ||
+		errors.Is(err, io.ErrClosedPipe) ||
+		(errors.As(err, &neterr) && !neterr.Timeout()) ||
+		strings.Contains(err.Error(), "tls:")
 }
 
 type ErrorStatus struct { //nolint:errname // ErrorStatus is a type name not a variable.