cmd/upspin: make createsuffixeduser correctly output proquint
cmd/upspin: make createsuffixeduser correctly output proquint

Change-Id: I0fee608c02fb51e402da6c4b8005150927441f95
Reviewed-on: https://upspin-review.googlesource.com/13880
Reviewed-by: Eric Grosse <3706282e8b8557d7b3733fe2b8fbbcffca452208@gmail.com>

upspin/upspin,upspin/upspin