Have disk and string list helpers print trailing newlins consistently

Have disk and string list helpers print trailing newlins consistently

In practise, omitting \n is pointless in get_*devs*(), addel() and rmel()
as they are all all used in such a way that the shell always ensures a
trailing \n anyway.
(This might have been needed with the old recursive bsort(), but not now.)

The one exception being the case of a ramdisk with no disks, which revealed
\n mishandling in the root disk question where it ought to print "none"
instead of an empty list of available disks (since inception in r1.1114):
	Available disks are: .
	Which disk is the root disk? ('?' for details) ?

OK afresh1