* Refactored `umount_all` to get the list of folders to be umounted from
`umount_all_list`, so we can test that function in a test case.
* Adjusted `umount_all_list` to return the deep folder levels first
* Added a testcase for that
* Remove redundant calls to `umount_all()` (which were from a time before
`pmbootstrap` was released, in which failing commands did not cause
`pmbootstrap` to raise an exception)
I've had a strange case where `cryptsetup status` did not work
inside the chroot anymore, and only zapping it would resolve it.
But I couldn't zap, because the status check was preventing shutdown
(on which zap depends) from working. This commit works around that.