SDL sometimes doesn't send BC.OnAppUnregistered in case HMI close an app with RESOURCE_CONSTRAINT reason

[GetmanetsIrina]

Bug Report

SDL sometimes doesn't send BC.OnAppUnregistered in case HMI close an app with RESOURCE_CONSTRAINT reason.

Occurrences

~0.5-0.9%

Reproduction Steps

1. SDL and HMI are started
2. App is registered on default mobile connection
3. App is activated
4. HMI sends BC.OnExitApplication with reason: RESOURCE_CONSTRAINT related to App to SDL

Expected Behavior

SDL sends BC.OnAppUnregistered notification to HMI

Observed Behavior

SDL doesn't send a notification to HMI

OS & Version Information

• OS/Version: Ubuntu 18.04
• SDL Core Version: https://github.com/smartdevicelink/sdl_core/tree/develop (b74c738)
• Testing Against: ATF:develop

Test Case, Sample Code, and / or Example App

• ATF Script: 025_OnExitApplication_RESOURCE_CONSTRAINT_one_app - needs to me run 1000 times
• Report and Logs: 0021.tar.gz

[GetmanetsIrina]

This is the same issue as #3561 from the scope of 8.1 release,
but I can see this issue on the current develop branch (b74c738).
On my environment, this issue is reproduced about ~2% on the 8.0.0 release
and about ~0.5-0.9% on the current develop branch

[GetmanetsIrina]

Luxoft team is going to prepare a fix