text/template: check final value for short-circuit and/or

text/template: check final value for short-circuit and/or

There was a bug in the short-circuit code for and/or added in CL 321490:
it ignored the value passed in by an earlier pipeline.

For #31103

Change-Id: Ic31f4d7cedfe563ef968cbb712ecfb2413c42eb5
Reviewed-on: https://go-review.googlesource.com/c/go/+/353130
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>