fmt: always clear wrapErrs

Like panicking and erroring - wrapErrs should always be reset to
the default false. wrapErrs should only be true when set by Errorf.

Change-Id: I4d51cc2f0905109e232b0983dc5331bd34f138bc
Reviewed-on: https://go-review.googlesource.com/c/go/+/178517
Run-TryBot: Martin Möhrmann <moehrmann@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>

src/fmt/print.go

@@ -122,7 +122,7 @@ type pp struct {
 	panicking bool
 	// erroring is set when printing an error string to guard against calling handleMethods.
 	erroring bool
-	// wrapErrors is set when the format string may contain a %w verb.
+	// wrapErrs is set when the format string may contain a %w verb.
 	wrapErrs bool
 	// wrappedErr records the target of the %w verb.
 	wrappedErr error
@@ -137,6 +137,7 @@ func newPrinter() *pp {
 	p := ppFree.Get().(*pp)
 	p.panicking = false
 	p.erroring = false
+	p.wrapErrs = false
 	p.fmt.init(&p.buf)
 	return p
 }