yaz-client: show uses last position if omitted
yaz-client: show uses last position if omitted

The show command has always used last position if omitted - except
that this was messed up in YAZ 4.0.2.

nla/yaz,nla/yaz,dcrossleyau/yaz,nla/yaz,dcrossleyau/yaz,dcrossleyau/yaz,nla/yaz