fix: allow explicit disable of placement with empty host

[inishchith]

Description

• This PR fixes a behavior where passing an explicitly empty placement host address should disable Placement, but instead the runtime still attempted to connect. It also aligns the CLI behavior and help so that users can reliably disable Placement without actors/workflows.

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: fixes: dapr/dapr#9000

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Extended the documentation

[inishchith]

@yaron2 @JoshVanL - possible to take a look?

[JoshVanL]

Hi @inishchith sorry to be slow on this!

This looks good to me.

We want to merge this into release-1.16 to be part of the next release. Changing base on GitHub pulls in things we don't want- I have opened up a PR with your changes&credit here, which will need a maintainer to approve since I'm a co-author.

If you're keen, you could do that yourself- branch from release-1.16 and cherry-pick these commits, and PR. I can then approve and merge for you.

Thanks again for this.

[inishchith]

hi @JoshVanL - thanks for taking a look.

I have opened a PR (#1535) as it'd be convenient with your context on this.