go.tools/dashboard/app: silence solaris11 and dragonfly builders

LGTM=aram, minux.ma
R=minux.ma, jsing, ality, aram, 0intro
CC=golang-codereviews
https://golang.org/cl/69980045

app/build/notify.go

@@ -33,10 +33,11 @@ const (
 // ignoreFailure is a set of builders that we don't email about because
 // they are not yet production-ready.
 var ignoreFailure = map[string]bool{
-	"dragonfly-amd64":       true,
-	"netbsd-amd64-bsiegert": true,
-	"plan-386-cnielsen":     true,
-	"solaris-amd64-smartos": true,
+	"dragonfly-386":           true,
+	"dragonfly-amd64":         true,
+	"netbsd-arm-rpi":          true,
+	"solaris-amd64-smartos":   true,
+	"solaris-amd64-solaris11": true,
 }
 
 // notifyOnFailure checks whether the supplied Commit or the subsequent