fix(mqtt-ad): change default for central scene value_template

[ccutrer]

to be a number, not a string, since it's a number data type now

refs #3570

tested against openHAB and Home Assistant

[coveralls]

Pull Request Test Coverage Report for Build 7769538201

• 0 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 22.076%

---

Totals
Change from base Build 7738176768:	0.0%
Covered Lines:	3763
Relevant Lines:	18124

---

💛 - Coveralls

[ccutrer]

ugh, this won't work. 0 is a valid scene id. I'll look into it more tomorrow

[kpine]

The original change was to add state_class, what does that accomplish exactly?

Anything done here, except for allowing a None value, breaks previous behavior, no?

[ccutrer]

Anything done here, except for allowing a None value, breaks previous behavior, no?

Indeed. I did attempt to not have a default at all, so that None would flow through, but Home Assistant logs a warning, and interprets it as 0 (which is what made me think to set the default to 0 for this PR). The original addition of state_class was simply done as a "hey, while I'm looking at Central Scene (because I'm getting a read-only entity for something that should be read/write), it's a number anyway, and it would be good to have it treated as such." That's not really a super-important goal if it causes other issues, and I agree that those issues with having no value are not worth that trade-off. I'll send a new PR to revert just the state_class portion.

[ccutrer]

See #3582