Fix mounting the fake cache area and unmounting the real container area

With these changes, the fake cache is correctly mounted on the Volla Phone and the Pixel 3a even when no fake cache existed before the boot. Since these devices have different states of /android/cache/ on boot (the Pixel 3a has a symlink to /data/cache, the Volla Phone has a directory), this seems quite good.

Still untested on the Xperia X, which would be appreciated.