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

pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,tv42/old-go