Fix does not send UnsubscribeVehicleData request to HMI after last unregister app.#2

IGapchuk wants to merge 3 commits intobranch_4.2.1IGapchuk/sdl_core:branch_4.2.1from

4.2.1.fix/sdl_not_send_UnsubscribeVehicleDataIGapchuk/sdl_core:4.2.1.fix/sdl_not_send_UnsubscribeVehicleDataCopy head branch name to clipboard