Allow "adb remount" on deduplicated filesystems to reboot into recovery
and run e2fsck to undo deduplication. The e2fsck binary is copied from
the system partition into tmpfs, and the system partition is unmounted
so e2fsck can run safely.
Bug: 64109868
Test: recovery with --fsck_unshare_blocks; adb remount
Change-Id: I7558749b018b58f3c4339e51a95831dbd5be1ae3
