The test currently expects all reader slots to be populated. This means
the cards may plugged into a random order, but there may not be any empty
slots in the system at all. This requirement is easy to meet when each
card has its own single-slot USB PCSC-reader, but as soon as multislot
readers are used there may be some empty slots.
Related: OS#6532
Change-Id: I7ba1d1350b6998d65e90408184accdb212556a7c
33256ddfed