Fix startup broken by #577

[puddly]

577 reorganized startup to allow for a simpler runtime reset (required for rebooting after writing config) but unfortunately omitted calls to register_endpoints and write_config, severely breaking it. This PR should address this.

CC @TheJulianJES

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.04% :tada:

Comparison is base (21cd029) 99.79% compared to head (b6478b7) 99.83%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## dev #578 +/- ## ========================================== + Coverage 99.79% 99.83% +0.04% ========================================== Files 68 68 Lines 4856 4858 +2 ========================================== + Hits 4846 4850 +4 + Misses 10 8 -2 ``` | [Files Changed](https://app.codecov.io/gh/zigpy/bellows/pull/578?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy) | Coverage Δ | | |---|---|---| | [bellows/zigbee/application.py](https://app.codecov.io/gh/zigpy/bellows/pull/578?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=zigpy#diff-YmVsbG93cy96aWdiZWUvYXBwbGljYXRpb24ucHk=) | `100.00% <100.00%> (+0.38%)` | :arrow_up: |

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[TheJulianJES]

Yep, seems to have fixed the issue 🎉