Don't allow badly formed upnp devices to kill auto discovery (#30342)
Prevent the following from occurring:
```
2019-12-31 22:38:41 ERROR (MainThread) [homeassistant.core] Error doing job: Task exception was never retrieved
Traceback (most recent call last):
File "/usr/src/homeassistant/homeassistant/data_entry_flow.py", line 85, in async_init
return await self._async_handle_step(flow, flow.init_step, data)
File "/usr/src/homeassistant/homeassistant/data_entry_flow.py", line 145, in _async_handle_step
result: Dict = await getattr(flow, method)(user_input)
File "/usr/src/homeassistant/homeassistant/components/deconz/config_flow.py", line 182, in async_step_ssdp
if discovery_info[ssdp.ATTR_UPNP_MANUFACTURER_URL] != DECONZ_MANUFACTURERURL:
KeyError: 'manufacturerURL'
2019-12-31 22:38:41 ERROR (MainThread) [homeassistant.core] Error doing job: Task exception was never retrieved
Traceback (most recent call last):
File "/usr/src/homeassistant/homeassistant/data_entry_flow.py", line 85, in async_init
return await self._async_handle_step(flow, flow.init_step, data)
File "/usr/src/homeassistant/homeassistant/data_entry_flow.py", line 145, in _async_handle_step
result: Dict = await getattr(flow, method)(user_input)
File "/usr/src/homeassistant/homeassistant/components/deconz/config_flow.py", line 182, in async_step_ssdp
if discovery_info[ssdp.ATTR_UPNP_MANUFACTURER_URL] != DECONZ_MANUFACTURERURL:
KeyError: 'manufacturerURL'
```