Atp concurrency improvements (#92)

* Fix many syncronization issues

There is a problem with closing

* Fix deadlock and switch to Cond variables

* Update terminology

* Addressed review comments and linter error

* Addressed review comments

* Remove nolint directive

* Addressed review comments

* Fixed linting error

* Add timeout for message sending

* Fix missing lock, and address review comments

* Addressed review comments

* Update comment