Investigate and fix uvloop-specific terminal app error

[achimnol]

The following error happens randomly (quite frequently) on start up of python -m ai.backend.kernel git:

shell-kernel: Fatal error on transport ReadUnixTransport (error status in uv_stream_t.read callback)
protocol: <ai.backend.kernel.terminal.StdoutProtocol object at 0x7f184ae94cf8>
transport: <ReadUnixTransport closed=False reading=False 0x7f184ae97298>
OSError: [Errno 5] Input/output error
opened shell pty: stdin at port 2002, stdout at port 2003
shell-kernel: Task exception was never retrieved
future: <Task finished coro=<Terminal.terminal_in() done, defined at /home/joongi/backend.ai-kernel-runner/ai/backend/kernel/terminal.py:136> exception=RuntimeError('read called while another coroutine is already waiting for incoming data',)>
Traceback (most recent call last):
  File "/home/joongi/backend.ai-kernel-runner/ai/backend/kernel/terminal.py", line 139, in terminal_in
    data = await self.sock_term_in.read()
  File "/home/joongi/.pyenv/versions/bai-kernel-runner-dev/lib/python3.6/site-packages/aiozmq/stream.py", line 278, in read
    raise RuntimeError('read called while another coroutine is '
RuntimeError: read called while another coroutine is already waiting for incoming data

and also another error in terminating:

shell-kernel: Fatal error on transport ReadUnixTransport (error status in uv_stream_t.read callback)
protocol: <ai.backend.kernel.terminal.StdoutProtocol object at 0x7f88dccedcc0>
transport: <ReadUnixTransport closed=False reading=False 0x7f88dccf0298>
OSError: [Errno 5] Input/output error

If I don't use uvloop, then it works fine.

[achimnol]

Let's drop aiozmq and update pyzmq/uvloop to latest versions.