Patch creates unwanted overlay when CRDs have an upstream

[joshmeranda]

Introduced in #129 when running make patch on a chart with a CRD chart that pulls from an upstream source, an unexpected generated-changes/overlay/crds is created. While this does not affect make prepare because we delete the CRDs from the main chart, this does clutter the generated-changes directory with unnecessary files and requires developers manually removing the directory after each make patch to avoid this.

To Reproduce

> git switch dev-v2.9
Switched to branch 'dev-v2.9'
Your branch is up to date with 'origin/dev-v2.9'.
> USE_CACHE=1 PACKAGE=rancher-monitoring/rancher-monitoring make prepare
...
> USE_CACHE=1 PACKAGE=rancher-monitoring/rancher-monitoring make patch
...
> git status
On branch dev-v2.9
Your branch is up to date with 'origin/dev-v2.9'.

Untracked files:
  (use "git add <file>..." to include in what will be committed)
        packages/rancher-monitoring/rancher-monitoring/charts-crd/
        packages/rancher-monitoring/rancher-monitoring/charts/
        packages/rancher-monitoring/rancher-monitoring/generated-changes/overlay/crds/

nothing added to commit but untracked files present (use "git add" to track)

[nicholasSUSE]

Resolved by this: #130