Milo: Use custom config caching layer

milo/appengine/buildbucket/builder.go

Index: milo/appengine/buildbucket/builder.go
diff --git a/milo/appengine/buildbucket/builder.go b/milo/appengine/buildbucket/builder.go
index 2b6ab94bdb91510b225efabfa8b86e6392054fb4..256b171a6f7ff85737bfbd845ae7f8979f6e7dee 100644
--- a/milo/appengine/buildbucket/builder.go
+++ b/milo/appengine/buildbucket/builder.go
@@ -229,13 +229,9 @@ type builderQuery struct {
 // builderImpl is the implementation for getting a milo builder page from buildbucket.
 // if maxCompletedBuilds < 0, 25 is used.
 func builderImpl(c context.Context, q builderQuery) (*resp.Builder, error) {
-	settings, err := common.GetSettings(c)
-	if err != nil {
-		logging.WithError(err).Errorf(c, "failed to get settings")
-		return nil, err
-	}
+	settings := common.GetSettings(c)
 	if settings.Buildbucket == nil || settings.Buildbucket.Host == "" {
-		logging.WithError(err).Errorf(c, "missing buildbucket settings")
+		logging.Errorf(c, "missing buildbucket settings")
 		return nil, errors.New("missing buildbucket settings")
 	}
 	host := settings.Buildbucket.Host