Fix OwnTracks deadlocking

[balloob]

Description:

When people had manually configured the owntracks platform, we got a circular dependency and deadlock.

Example entry for configuration.yaml (if applicable):

device_tracker:
  platform: owntracks

# owntracks config entry.

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[raccettura]

Tried this but there might still be a problem. I've now got owntracks working with the http webhook. If I remove my device from known_devices.yml it will re-add itself.

I then tried adding the following to my config:

owntracks:
  max_gps_accuracy: 150
  waypoints: true
  events_only: true
  waypoint_whitelist:
    - raccettura
  region_mapping:
    home: home
    work: work

Then restarted and made owntracks update my location. No device was added to known_devices.yml. Accuracy was +/- 65m... which is well under 150 I'm specifying. I even upped it to 200.

Remove the config and once again I get a device added to known_devices.yml.