Create, mount and unmount app data mirror directory

- When volume is ready, system/installd will
create app data mirror, and bind mount it the actual CE storage for
that app.

- When a new private volume is mounted, DE mirror will be created and
mounted.

- When a private volume is unmounted, all users CE mirror will be
unmounted and DE mirror will be unmounted also.

- Fix inode createAppData() return a wrong inode number in 32bit system.

Bug: 143937733
Bug: 145989852
Test: After reboot, all apps mirror CE directories are created and
mounted
Test: After adding a new private volume, new CE DE mirror for that volume
are created and mounted.
Test: After unmounting a private volume, that vol CE DE mirror are
unmounted.
Change-Id: I8a06ae8917e5f2c7f1f905b73ec934de7f1ee802