Connect response wrong hpai

[Julius2342]

Trying to fix #76 and home-assistant/core#24492

@farmio : is this how you thought it should be solved?

[coveralls]

Coverage increased (+0.008%) to 91.828% when pulling fe0f414 on Julius2342:connect-response-wrong-hpai into cc10a82 on XKNX:master.

[farmio]

so this is what I get when I test it now:

DEBUG:xknx.knx:Received: <KNXIPFrame <KNXIPHeader HeaderLength="6" ProtocolVersion="16" KNXIPServiceType="KNXIPServiceType.CONNECT_RESPONSE" Reserve="0" TotalLength="8" />
 body="<ConnectResponse communication_channel="0" status_code="ErrorCode.E_NO_MORE_UNIQUE_CONNECTIONS" control_endpoint="<HPAI 0.0.0.0:0 />" request_type="None" identifier="None" />" />
WARNING:xknx.log:Error: KNX bus responded to request of type 'Connect' with error in 'ConnectResponse': ErrorCode.E_NO_MORE_UNIQUE_CONNECTIONS
Traceback (most recent call last):
  File "/Users/meti/Documents/Dev/xknx-xknx/xknx/main.py", line 51, in <module>
    loop.run_until_complete(main())
  File "/usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/asyncio/base_events.py", line 584, in run_until_complete
    return future.result()
  File "/Users/meti/Documents/Dev/xknx-xknx/xknx/main.py", line 40, in main
    await xknx.start(connection_config=connection_config)
  File "/Users/meti/Documents/Dev/xknx-xknx/xknx/xknx/xknx.py", line 76, in start
    await self.knxip_interface.start()
  File "/Users/meti/Documents/Dev/xknx-xknx/xknx/xknx/io/knxip_interface.py", line 102, in start
    self.connection_config.auto_reconnect_wait)
  File "/Users/meti/Documents/Dev/xknx-xknx/xknx/xknx/io/knxip_interface.py", line 144, in start_tunnelling
    await self.interface.start()
  File "/Users/meti/Documents/Dev/xknx-xknx/xknx/xknx/io/tunnel.py", line 83, in start
    await self.connect()
  File "/Users/meti/Documents/Dev/xknx-xknx/xknx/xknx/io/tunnel.py", line 104, in connect
    raise XKNXException("Could not establish connection")
xknx.exceptions.exception.XKNXException: Could not establish connection

That's far better than before 👍

Should we catch the error somewhere and exit gracefully?

[farmio]

home-assistant/core#15313 could profit from this as well.