test: fix racy test ReaderNoFollow

Due to the race between `Read()` and context cancellation, error might
be returned which we can safely ignore.

Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>

internal/pkg/kmsg/reader_test.go

@@ -6,6 +6,7 @@ package kmsg_test
 
 import (
 	"context"
+	"errors"
 	"os"
 	"testing"
 	"time"
@@ -82,6 +83,13 @@ LOOP:
 				break LOOP
 			}
 
+			if closed && errors.Is(packet.Err, os.ErrClosed) {
+				// ignore 'file already closed' error as it might happen
+				// from the branch below depending on whether context cancel or
+				// read() finishes first
+				continue
+			}
+
 			assert.NoError(t, packet.Err)
 
 			messageCount++