Guard bad entity ID in entity registry

[balloob]

Breaking change

Proposed change

We changed the entity ID format last year. I just came across a stack trace from a user that still had bad entities crashing the state restoration of the entity registry.

This PR fixes it.

2020-05-05 12:58:58 ERROR (MainThread) [homeassistant.core] Error doing job: Exception in callback async_setup_entity_restore.<locals>._write_unavailable_states(<Event homeassistant_start[L]>) at /usr/src/homeassistant/homeassistant/helpers/entity_registry.py:572
Traceback (most recent call last):
  File "/usr/local/lib/python3.7/asyncio/events.py", line 88, in _run
    self._context.run(self._callback, *self._args)
  File "/usr/src/homeassistant/homeassistant/helpers/entity_registry.py", line 604, in _write_unavailable_states
    states.async_set(entry.entity_id, STATE_UNAVAILABLE, attrs)
  File "/usr/src/homeassistant/homeassistant/core.py", line 994, in async_set
    state = State(entity_id, new_state, attributes, last_changed, None, context)
  File "/usr/src/homeassistant/homeassistant/core.py", line 736, in __init__
    f"Invalid entity id encountered: {entity_id}. "
homeassistant.exceptions.InvalidEntityFormatError: Invalid entity id encountered: media_player.tclroku_tv__2n006r392241. Format should be <domain>.<object_id>

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
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