This commit includes efficiency improvements in two places in the
database/sql package where an "if err != nil" was redundant and
the error can be returned as-is (most of the code in the standard
library and even in the file I changed does it my suggested way).

Change-Id: Ib9dac69ed01ee846e570a776164cb87c2caee6ca
Reviewed-on: https://go-review.googlesource.com/106555Reviewed-by: Daniel Theophanes <kardianos@gmail.com>
Run-TryBot: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>