Allow Rescue Partition Without Breaking USB Boot

[gbourass]

Having a rescue system on the EFI partition can be useful. However it is detected by nlplug-findfs and breaks your USB/CD boot. If it is hidden far enough it doesn't interfere with USB/CD boot. However, when nlplug-findfs doesn't find an apkovl or an apks in a device it unmounts it after the search. The parameters ovl_dev and alpine_dev are no longer used. Automatically remounting explicit media references in apkovl and alpine_repo makes it possible without effort to explicitly use hidden from nlplug-findfs apks and apkovl. E.G.: apkovl=/media/sda1/boot/rescue/apkovl.tar.gz

[gbourass]

Another use case handled by this fix is as follow: If you boot a server (EFI) from the Alpine ISO/CD and then just FAT format an HDD on the server and copy everything from the CD as is on the HDD, you have a bootable server. Sweet! Everything looks fine until you try to boot again from the CD. You will see (using mount) that you actually used the apks and apkovl from the HDD even if you loaded Grub from the CD. If the content on the CD is different (a new version), you have not loaded what you wanted. With this fix, you could simply hide the apks/apkovl deeper in the HDD directories to avoid discovery and breaking the media boot and set your apkolv and alpine_repo as boot parameters in your grub menu entry to allow booting from the HDD.