Linux platform wifiIPThread resource leak

[msandstedt]

Problem

From this rev:

commit ab665728d96a946ef3d6e2715784b7dbc0f6a3eb
Author: Andrei Litvin <[email protected]>
Date:   Sat Aug 21 10:49:52 2021 -0400

And this file:

platform/Linux/PlatformManagerImpl.cpp

This code spawns and detaches this thread, and keeps no reference to it:

CHIP_ERROR PlatformManagerImpl::_InitChipStack()
...
    std::thread wifiIPThread(WiFIIPChangeListener);
    wifiIPThread.detach();

This is effectively a resource leak. It's impossible to cleanup this thread and, so each InitChipStack leaks another thread. This also presumably makes orderly shutdown impossible. WiFIIPChangeListener may never stop posting work to the event event queue.

Proposed Solution

• Linux platform must retain a reference to the spawned wifiIPThread
• Linux platform requires a symmetric _Shutdown method
• the _Shutdown method must signal to the wifiIPThread and then join it

[msandstedt]

@samadDotDev, @z-michel, @kpschoedel, @pan-apple