Do not throw on race-condition when creating client JS directory

[evantahler]

Closes #1965

This PR use fs.mkdirSync(path, { recursive: true }); to not throw if there was a race condition with 2 actionhero processes trying to create the client js lib's directory at the same time. This was likely to happen in fast tests.

$ node
Welcome to Node.js v16.6.1.
Type ".help" for more information.

> const fs = require('fs')
undefined
> fs.mkdirSync('/tmp/foo')
undefined
> fs.mkdirSync('/tmp/foo')
Uncaught Error: EEXIST: file already exists, mkdir '/tmp/foo'
    at Object.mkdirSync (node:fs:1324:3) {
  errno: -17,
  syscall: 'mkdir',
  code: 'EEXIST',
  path: '/tmp/foo'
}
> fs.mkdirSync('/tmp/foo', {recursive: true})
undefined