Refactor: Use common.expectsError in tests

[mithunsasidharan]

Refactored tests to replace assert.throws(fn, common.expectsError(err)); with common.expectsError(fn, err); in following test files :

• test/parallel/test-dns.js
• test/parallel/test-fs-realpath.js
• test/parallel/test-fs-watchfile.js
• test/parallel/test-http-client-check-http-token.js
• test/parallel/test-http-client-reject-unexpected-agent.js
• test/parallel/test-http-client-unescaped-path.js
• test/parallel/test-http-hostname-typechecking.js
• test/parallel/test-http-request-invalid-method-error.js
• test/parallel/test-http-response-statuscode.js
• test/parallel/test-http-server-de-chunked-trailer.js
• test/parallel/test-http-write-head.js

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

test

[BridgeAR]

LGTM but the commit message should start with the test subsystem.

[apapirovski]

@mithunsasidharan FWIW, feel free to just open one big pull request if you're doing this for the rest of the tests. It will make it easier to land it and it's really not that hard to review, even if it's 100+ files.

(Less to keep track of for backports too.)

[cjihrig]

Also, be prepared to backport all of these PRs to other release lines.

[maclover7]

CI: https://ci.nodejs.org/job/node-test-pull-request/11931/

[apapirovski]

Landed in acd4277