SDL sends wrong SubscribeButton response with UNSUPPORTED_RESOURCE, success:false in case HMI responds UI.IsReady with "available" = false

[VjKlepikov]

Bug Report

SDL sends wrong SubscribeButton response with UNSUPPORTED_RESOURCE, success:false in case HMI responds UI.IsReady with "available" = false

Reproduction Steps

1. SDL and HMI are started.
2. HMI respond with 'available' = false on UI.IsReady request from SDL
3. App is registered and activated
4. App requests SubscribeButton with Button part to SDL

Expected Behavior

SDL sends Buttons.SubscribeButton request to HMI
SDL responds SubscribeButton(resultCode: SUCCESS, success: true) to App

Observed Behavior

SDL does not send Buttons.SubscribeButton request to HMI
SDL responds SubscribeButton(resultCode: UNSUPPORTED_RESOURCE, success: false) to App

OS & Version Information

OS/Version: Ubuntu 18.04
SDL Core Version: https://github.com/smartdevicelink/sdl_core/tree/develop (65947fd)

Logs:

SubscribeButton.zip