Update how to identify the docker error

Co-authored-by: Jaime Soriano Pastor <jaime.soriano@elastic.co>

Author: mrodm

internal/testrunner/runners/system/tester.go

@@ -1748,7 +1748,8 @@ func (r *tester) runTest(ctx context.Context, config *testConfig, stackConfig st
 	if err != nil {
 		// Known issue: do not include this as part of the xUnit results
 		// Example: https://buildkite.com/elastic/integrations/builds/22313#01950431-67a5-4544-a720-6047f5de481b/706-2459
-		if strings.Contains(err.Error(), "fork/exec /usr/bin/docker: operation not permitted") {
+		var pathErr *fs.PathError
+		if errors.As(err, &pathErr) && pathErr.Op == "fork/exec" && pathErr.Path == "/usr/bin/docker" {
 			return result.WithError(err)
 		}
 		// report all other errors as error entries in the xUnit file