Fix/3178 crash on shutdown

[LuxoftAKutsan]

Fixes #3178

This PR is ready for review.

Risk

This PR makes no API changes.

Testing Plan

Script should be created.

Summary

We used aggregation in Thread class and we dont have contorol over
delegate life cycle, so logically need first to delete container and then delete delegate.
we are calling join() -> stop() Inside destuctor of Thread
we are using delegate_->exitThreadMain(); Inside the stop()

Shutdown () was removed because it is redundant. Destructor Thread will make this.


The core crash shows evidence that something around set_delegate is
crashing, on the other hand ~MessageLoopThread is deleting the thread
and not assigning the thread pointer to NULL which is necessary to avoid
undefined behavior

Tasks Remaining:

• Create script for the issue
• Internal Luxoft review
• Check regression

CLA

• I have signed the CLA

[AByzhynar]

@LuxoftAKutsan In the PR description you have stated the following:

Shutdown () was removed because it is redundant.

As I can see it was not removed. Remove it please or change PR description.

[AByzhynar]

@LuxoftAKutsan Why did you set thread_ pointer to NULL after deletion but did not set thread_delegate_ to NULL after deletion? It is a pointer as well.

[Jack-Byrne]

Potential related fix #3388

[iCollin]

Thread delegates must be destroyed before threads.

Otherwise, when the delegate is destroyed it will attempt to write on the thread pointer that has been deleted.

ThreadDelegate::~ThreadDelegate() {
  if (thread_) {
    thread_->set_delegate(NULL);
  }
}

[jacobkeeler]

Thread delegate must be deleted before the thread itself. All threads in the project follow this pattern

[theresalech]

@LuxoftAKutsan, can you please let us know when this is ready for re-review?

[LuxoftAKutsan]

@theresalech this work is planned. We will notify when fix with test scripts will be available.

[LuxoftAKutsan]

Agree with PM comments.

Tested attached script on current develop looks like issued covered with #3388 fix.