internal/config: fix the GetEnvInt, GetEnvFloat
internal/config: fix the GetEnvInt, GetEnvFloat

GetEnvInt & GetEnvFloat should return the calculated value if err is
nil.

Change-Id: I84e7d96314f83792b13143a6f737162cb5e65839
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/247857
Reviewed-by: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>
Run-TryBot: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>
TryBot-Result: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite