[CMFileManager] Fix the DrawerLayout don't disapper after press back key.

Procedures
1.Go into filemanager and enter a directory(such as Music).
2.Open the menu Button in the top left corner and popup the drawerlayout.
3.press the back key.

The DrawerLayout don't disapper and the navigation view back to the next higher level.

Change-Id: I13c78491e2be767e7611d57c2c513013d96465eb