Switch from `chroot` to `switch_root`

[cmhe]

The init script is currently using chroot, that means that the original initrd will not be unloaded.

switch_root is doing this correctly.

[gil0109]

@cmhe Do you have this working with Rocko branch?

[cmhe]

@gil0109 I don't see why not. But please try it out and report.

Because its a pretty small layer, I normally use not as a dependency, but integrate it into bigger customer specific layers where further customization is done on these scripts.