initramfs-error-handling: init-premount mdadm hook script does not get executed.

[Luke Yelavich]

Binary package hint: mdadm

The init-premount script which was added as part of the initramfs error handling spec does not get executed, due to the script only being useful when a root device cannot be found, and information needs to be displayed to the user as to how they could fix the problem. This doesn't work due to the md device already existing by the time it comes to check whether a root device exists. The boot eventually fails even with a degraded array, and no information is displayed to the user as to how they could fix their setup.