Core/Misc: Fix current player state when logging out

Sit should only be apply'd when player is standing.
For example when sitting on a chair when logging out, player should stay on the chair until fully logged out and not sit on the floor.
Merge pull request #13321 from Kittnz/unit_state

Core/Misc: Fix current player state when logging out
Merge branch 'master' of https://github.com/TrinityCore/TrinityCore into ghbb