[release-branch.go1.2] database/sql: Use all connections in pool

««« CL 40410043 / 8a7ac002f840
database/sql: Use all connections in pool

The last connection in the pool was not being handed out correctly.

R=golang-codereviews, gobot, bradfitz
CC=golang-codereviews
https://golang.org/cl/40410043

»»»

LGTM=r
R=golang-codereviews, r
CC=golang-dev
https://golang.org/cl/68820044