[ember] Fix coordinator-only permit join

[Nerivec]

Logic should now follow UI descriptions properly:

• All -> Coordinator + broadcast
• Coordinator -> Coordinator only (previously was the equivalent of selecting All)
• Device XYZ -> Device XYZ only

Thanks to @wastez for using the exact words needed to point me in the direction of this one, even though it doesn't solve the problem we were tackling at the time 😉

Tested/working as expected.

[Koenkk]

Thanks!