test: fix test-cluster-concurrent-disconnect

The error code, `ECONNRESET`, is observed on linux.
This commit adds it as an expected error code.

Signed-off-by: Daeyeon Jeong daeyeon.dev@gmail.com

PR-URL: #43961
Refs: https://ci.nodejs.org/job/node-test-commit-linux-containered/nodes=ubuntu1804_sharedlibs_withoutintl_x64/32901/testReport/junit/(root)/test/parallel_test_cluster_concurrent_disconnect/
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
Reviewed-By: Feng Yu <F3n67u@outlook.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>

test/parallel/test-cluster-concurrent-disconnect.js

@@ -29,7 +29,7 @@ if (cluster.isPrimary) {
       if (common.isOSX) {
         assert(['EPIPE', 'ENOTCONN'].includes(err.code), err);
       } else {
-        assert.strictEqual(err.code, 'EPIPE');
+        assert(['EPIPE', 'ECONNRESET'].includes(err.code), err);
       }
     });