Copy parsed flag values when constructing `LocalFlags()`

[bcongdon]

This checks in the failing test that #1019 references, and proposes a fix to LocalFlags() not copying information about whether a flag has been parsed or not.

If preferable, I can open a PR against spf13/pflag to change flagSet.AddFlag to copy the fact that a flag already has a value instead of performing that logic here.

[CLAassistant]

All committers have signed the CLA.

[github-actions[bot]]

This PR is being marked as stale due to a long period of inactivity

[bcongdon]

Pinging this, CLA is signed

[johnSchnake]

I'm so sorry its taken so long to respond to this PR. We are actively trying to tackle the backlog.