[Tests] Test on linux randomly fails with "Failed: Timeout"

[drew2a]

Error Message

Failed: Timeout >20.0s

Stacktrace

kwargs = {'channel_seeder': <tribler.core.components.libtorrent.download_manager.download_manager.DownloadManager object at 0x7...r': <tribler.core.components.gigachannel_manager.gigachannel_manager.GigaChannelManager object at 0x7fef7c3d20a0>, ...}
coro = <coroutine object test_channel_update_and_download at 0x7fef7c5da3c0>
task = <Task pending name='Task-6109' coro=<test_channel_update_and_download() running at /home/jenkins/workspace/GH_Tribler_...nkins/.local/lib/python3.8/site-packages/ipv8/taskmanager.py:128, <TaskWakeupMethWrapper object at 0x7fef7c7e5bb0>()]>>

    @functools.wraps(func)
    def inner(**kwargs):
        coro = func(**kwargs)
        if coro is not None:
            task = asyncio.ensure_future(coro, loop=_loop)
            try:
>               _loop.run_until_complete(task)

../../../../.local/lib/python3.8/site-packages/pytest_asyncio/plugin.py:195: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/usr/lib/python3.8/asyncio/base_events.py:603: in run_until_complete
    self.run_forever()
/usr/lib/python3.8/asyncio/base_events.py:570: in run_forever
    self._run_once()
/usr/lib/python3.8/asyncio/base_events.py:1823: in _run_once
    event_list = self._selector.select(timeout)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <selectors.EpollSelector object at 0x7fef7c365130>, timeout = 0.963

    def select(self, timeout=None):
        if timeout is None:
            timeout = -1
        elif timeout <= 0:
            timeout = 0
        else:
            # epoll_wait() has a resolution of 1 millisecond, round away
            # from zero to wait *at least* timeout seconds.
            timeout = math.ceil(timeout * 1e3) * 1e-3
    
        # epoll_wait() expects `maxevents` to be greater than zero;
        # we want to make sure that `select()` can be called when no
        # FD is registered.
        max_ev = max(len(self._fd_to_key), 1)
    
        ready = []
        try:
>           fd_event_list = self._selector.poll(timeout, max_ev)
E           Failed: Timeout >20.0s

/usr/lib/python3.8/selectors.py:468: Failed

Jenkins console output
PR: #6821

[drew2a]

This behavior could be caused by parallel Jobs executions.
I disabled concurrent builds for Linux to observe will it have effect or not:

UPD: it doesn't help, Jenkins' settings have been reverted back.