[RPC] Fix tracker connection termination

[Icemist]

In a wireless connection situation (android example below) we have a device key containing a colon character(:).

ANDROID_SERIAL_NUMBER = 192.168.0.143:5555

C:\Users\icemist>docker exec -it ice_tvm_container adb devices
List of devices attached
192.168.0.143:5555     device

In this case we get an error:

ERROR:asyncio:Exception in callback None()
handle: <Handle cancelled>
Traceback (most recent call last):
  File "/usr/lib/python3.8/asyncio/events.py", line 81, in _run
    self._context.run(self._callback, *self._args)
  File "/venv/apache-tvm-py3.8/lib/python3.8/site-packages/tornado/platform/asyncio.py", line 206, in _handle_events
    handler_func(fileobj, events)
  File "/git/tvm/python/tvm/rpc/tornado_util.py", line 41, in _event_handler
    self._event_handler(events)
  File "/git/tvm/python/tvm/rpc/tornado_util.py", line 79, in _event_handler
    if self._update_read() and (events & self._ioloop.WRITE):
  File "/git/tvm/python/tvm/rpc/tornado_util.py", line 121, in _update_read
    self.close()
  File "/git/tvm/python/tvm/rpc/tornado_util.py", line 67, in close
    self.on_close()
  File "/git/tvm/python/tvm/rpc/tracker.py", line 298, in on_close
    self._tracker.close(self)
  File "/git/tvm/python/tvm/rpc/tracker.py", line 353, in close
    self._scheduler_map[rpc_key].remove(value)
KeyError: '127.0.0.1'

For example, test_rpc_tracker_via_proxy hangs if the device key format contains a colon.

The point is that the keys before using the split have a format like:
conn.put_value has: hexagon-dev.127.0.0.1:5555:0.513619
_tracker_pending_puts has: 127.0.0.1:5555:0.2809967317812382

[tvm-bot]

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[Icemist]

@echuraev @apeskov @areusch

[echuraev]

Please carefully update all using of the updated functions.

[echuraev]

LGTM. Thanks!