test: fix too optimistic guess in setproctitle

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

test, process

test/parallel/test-setproctitle.js assumes that process.title can't be test before the test changes it. However, if this test is launched as a child several times, process.title is saved in the parent on Windows and is shared with childs.

I've found this issue running tests with some script with different options. A reduced example (edit the path to reproduce):

const { execSync } = require('child_process');
const cmd = 'node j:/temp/_git/node-fork/test/parallel/test-setproctitle.js';

console.log('run 1');
try { execSync(cmd); } catch (err) { console.log('run 1 error'); }
console.log('run 2');
try { execSync(cmd); } catch (err) { console.log('run 2 error'); }

Before this PR:

run 1
run 2

assert.js:86
  throw new assert.AssertionError({
  ^
AssertionError: 'test' !== 'test'
    at Object.<anonymous> (j:\temp\_git\node-fork\test\parallel\test-setproctitle.js:19:8)
    at Module._compile (module.js:582:30)
    at Object.Module._extensions..js (module.js:593:10)
    at Module.load (module.js:516:32)
    at tryModuleLoad (module.js:466:12)
    at Function.Module._load (module.js:458:3)
    at Function.Module.runMain (module.js:618:10)
    at startup (bootstrap_node.js:144:16)
    at bootstrap_node.js:548:3
run 2 error

After this PR:

run 1
run 2

It seems this better be fixed to prevent such issues with various test approaches to test base.