New setting: Allow delaying background sync while playing videos

[Spacetech]

This is a follow up on #2027. While that change works, I still want to prevent background sync library refreshes (due to new media being added) from happening while playing videos.

The scheduled full sync code prevents it from running while videos are playing (link). I think we should allow the same for background sync.

Changes:

• Add a Delay background sync while media is playing setting to enable similar functionality for the background sync flow. It will essentially keep storing websocket messages and process them once you are no longer playing a video.
• Make the check for the refreshed property a little safer. I saw an error in my logs related to this.

[croneter]

May I ask: why? I personally never had any issues with the way it's working now

[Spacetech]

The skin I'm using displays a black flash at the top right of the screen when update_kodi_library is called. This even happens while I'm watching something. I think it's trying to indicate a refresh/something progressed, but it's very distracting.

This new setting is defaulting to false, so the existing behavior will remain the same unless someone opt's into it.

[croneter]

Thanks once again!! Merged with https://github.com/croneter/PlexKodiConnect/commit/3bf7ae1fd713fe6ee010dda142a8177c38c9ef25, your new setting now defaults to true :wink: