HMI doesn't send all BC.OnSystemRequest notifications during retry PTU

[TMyza]

Bug Report
Defect relevant for External flow.
"seconds_between_retries" parameter has 5 value in the array.
During retry PTU, HMI sends one less notification to SDL.
SDL can't finish PTU correctly.

Reproduction Steps

1. Start SDL, HMI, connect Mobile
2. App is consented and activated
3. PTU is finished, App has UP-TO-DATE status (without certificate)
4. Start security video stream, policy server not responding
5. SDL is started PTU retry sequence

Expected Behavior

1. HMI sends all BC.OnSystemRequest notification
2. SDL sends Nack to App

Observed Behavior

1. HMI doesn't send all BC.OnSystemRequest notification
2. SDL can't finish PTU correctly.
3. SDL doesn't send Nack to App.

OS & Version Information
sdl_hmi branch: develop
commit: e415fe4
sdl_core branch: https://github.com/smartdevicelink/sdl_core/tree/6.1.0_RC

[jacobkeeler]

@TMyza It looks like the sdl_hmi sends the correct number of OnSystemRequest notifications (in this case 6, one for the first attempt and 5 retries), the issue is with Core since it doesn't send the NACK after the last attempt times out. See smartdevicelink/sdl_core#3440