2.2/feature: reduce redundant find video steps

tower: https://tower.im/projects/d4e0ff64158645f28d99a9ca72d0c27b/todos/bf2e01c6ad5d40a0b733908cb16c5d65

by move find serie related operations from addPlaylistItem
to playPaths, it's all changed ;)

Change-Id: I786c989a6d8246164665e4e38854da6f83e296e8