Refactor deleting temp dirs into a loop

[dougireton]

This should be a loop.

The Windows bootstrap is shown below, but this also applies to Bash.

# Cleanup
if (Test-Path $berksfilePath) {
  Remove-Item $berksfilePath
}

if (Test-Path "$berksfilePath.lock") {
  Remove-Item "$berksfilePath.lock"
}

if (Test-Path $chefConfigPath) {
  Remove-Item $chefConfigPath
}

if (Test-Path nodes) {
  Remove-Item -Recurse nodes
}

if (Test-Path berks-cookbooks) {
  Remove-Item -Recurse berks-cookbooks
}

[dougireton]

This is solved for Mac by #86.

https://github.com/Nordstrom/chefdk_bootstrap/pull/86/files#diff-ca4c50b905dc21ea17a10549a6f5944fR113