[homekit] fix group handling

[yfre]

PR #7967 creates sometimes one accessory twice:
there are following cases that should be supported:

1. one accessory defined using group, light switch tagged as "OnState" characteristic

Group  gLight 	"Light Group" {homekit="Lighting"}
Switch light   "Light" (gLight) {homekit="OnState"}

2. one accessory defined using group, light switch tagged as "Lighting.OnState" characteristic

Group  gLight 	"Light Group" {homekit="Lighting"}
Switch light   "Light" (gLight) {homekit="Lighting.OnState"}

3. two accessories: first = group itself, second = switch (switch can be tagged as "Lighting" or "Lighting.OnState")

Group:Switch:OR(ON,OFF)  gLight "Light Group" {homekit="Lighting"}
Switch light   "Light" (gLight)  {homekit="Lighting..OnState"}

1. and 3) were working correctly, but in case of 2) it has created 2 accessories, one = group+switch, second = switch

this PR fixes the 2) case. all 3 cases are tested and working correctly. added comment describing the cases

Signed-off-by: Eugen Freiter freiter@gmx.de

[J-N-K]

Is this behavior properly documented in the README?

[yfre]

Is this behavior properly documented in the README?

it seems to be expected behaviour and it was working that way before. This PR fixes basically a bug.
but i have added an example to a README so that different ways of using groups are more clear.

[TravisBuddy]

Travis tests have failed

Hey @yfre,
please read the following log in order to understand the failure reason. There might also be some helpful tips along the way.
It will be awesome if you fix what is wrong and commit the changes.

[yfre]

@J-N-K i have updated the documentation. is anything else open here? i would love to merge this before 2.6.7 as it is pretty ugly bug

[J-N-K]

Travis fails in Java11 build while using SAT.