database/sql: fix test on 32-bit
database/sql: fix test on 32-bit

R=golang-codereviews
TBR=golang-dev
CC=golang-codereviews
https://codereview.appspot.com/49920047

apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang,apparentlymart/golang