runtime: don't report non-blocked goroutines as "(durable)" in stacks

Only append the " (durable)" suffix to a goroutine's status
when the goroutine is waiting.

Avoids reporting a goroutine as "runnable (durable)".

Change-Id: Id679692345afab6e63362ca3eeff16808367e50f
Reviewed-on: https://go-review.googlesource.com/c/go/+/705995
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Damien Neil <dneil@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

src/runtime/traceback.go

@@ -1249,6 +1249,7 @@ func goroutineheader(gp *g) {
 		print(" (scan)")
 	}
 	if bubble := gp.bubble; bubble != nil &&
+		gpstatus == _Gwaiting &&
 		gp.waitreason.isIdleInSynctest() &&
 		!stringslite.HasSuffix(status, "(durable)") {
 		// If this isn't a status where the name includes a (durable)