CMFileManager: Fix back press events of SearchActivity

epro:
- SearchActivity to audio file
- Open audio file with small player (e.g. Play Music)
- Press back
- Observe: audio player closes and CMFM SearchActivity up one directory(NavigationActivity)

Change-Id: I4ab1faa1d061eea97050b89e96c1bdf1df66db3f
(cherry picked from commit 336c3849)