fix: allow resource.Exec to correctly wait for process completion

[flowchartsman]

This bug was due to a bug in the vendored client library where StartExec would return early if stderr and stdout were not attached (even if opts.Detatch was false, which is the default. This fix always attaches them and falls back to io.Discard if the user does not provide their own readers.

• See: StartExec does not wait for process to finish if stdout/stderr not passed in fsouza/go-dockerclient#838

Related Issue or Design Document

Fixes #372

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact [email protected]) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

[flowchartsman]

Looks like my formatter/linter took a couple liberties with an import directive and some octal values. If this chafes, I can redo the PR without them.

[flowchartsman]

LOL, if I'd only submitted a few days earlier...
CVE-2022-32149
CVE-2021-38561

[flowchartsman]

I think this CI failure is spurious. Nancy doesn't complain when run from the repo with the current recommended invocation:

❯ go list -json -deps ./... | docker run --rm -i sonatypecommunity/nancy:latest sleuth
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I've filed a bug upstream.

[aeneasr]

Awesome, thank you! 🎉 Your contribution makes Ory better :)