runtime/pprof: enable profiling test on openbsd

Profiling of multithreaded applications works correctly on OpenBSD
5.4-current, so enable the profiling test.

R=golang-codereviews, minux.ma
CC=golang-codereviews
https://golang.org/cl/50940043

src/pkg/runtime/pprof/pprof.go

@@ -20,7 +20,7 @@ import (
 	"text/tabwriter"
 )
 
-// BUG(rsc): Profiles are incomplete and inaccuate on NetBSD, OpenBSD, and OS X.
+// BUG(rsc): Profiles are incomplete and inaccuate on NetBSD and OS X.
 // See http://golang.org/issue/6047 for details.
 
 // A Profile is a collection of stack traces showing the call sequences

src/pkg/runtime/pprof/pprof_test.go

@@ -274,7 +274,6 @@ func TestMathBigDivide(t *testing.T) {
 var badOS = map[string]bool{
 	"darwin": true,
 	"netbsd": true,
-	"openbsd": true,
 }
 
 func TestBlockProfile(t *testing.T) {