Fix yeelight recorder warning

[zewelor]

Description:

Fix for recorder warnings:

2019-04-05 08:33:08 WARNING (Recorder) [homeassistant.components.recorder] Event is not JSON serializable: <Event platform_discovered[L]: service=load_platform.light, platform=yeelight, discovered=name=Bedroom ceiling, model=ceiling2, transition=350, save_on_change=False, use_music_mode=False, host=192.168.1.136, custom_effects=Sunrise=count=1, action=Action.off, transitions=[<TemperatureTransition(1700K) duration 3000, brightness 10>, <TemperatureTransition(6500K) duration 3000, brightness 100>]> 

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.

[github-actions]

Hey there @rytilahti, @zewelor, mind taking a look at this pull request as its been labeled with a integration (yeelight) you are listed as a codeowner for? Thanks!

[codecov]

Codecov Report

Merging #22756 into dev will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev   #22756      +/-   ##
==========================================
+ Coverage   93.83%   93.83%   +<.01%     
==========================================
  Files         448      448              
  Lines       36523    36524       +1     
==========================================
+ Hits        34271    34272       +1     
  Misses       2252     2252

Impacted Files	Coverage Δ
homeassistant/components/hassio/ingress.py	71.05% <0%> (-0.26%)	⬇️
homeassistant/components/stream/worker.py	93.68% <0%> (+0.06%)	⬆️
homeassistant/components/hassio/http.py	88.23% <0%> (+0.17%)	⬆️

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