util-stats: full translation for BroadcastStatsReceiver

=== Problem
`BroadcastStatsReceiver` hides the underlying receivers' translation mode.

=== Solution
Just translate all metrics with `FullTranslation`.

Differential Revision: https://phabricator.twitter.biz/D1220816

Author: keremnc

util-stats/src/main/scala/com/twitter/finagle/stats/BroadcastStatsReceiver.scala

@@ -22,6 +22,9 @@ object BroadcastStatsReceiver {
       with DelegatingStatsReceiver {
     val repr: AnyRef = this
 
+    override def scopeTranslation: NameTranslatingStatsReceiver.Mode =
+      NameTranslatingStatsReceiver.FullTranslation
+
     def counter(metricBuilder: MetricBuilder) = new BroadcastCounter.Two(
       first.counter(metricBuilder),
       second.counter(metricBuilder)
@@ -63,6 +66,9 @@ object BroadcastStatsReceiver {
   private class N(srs: Seq[StatsReceiver]) extends StatsReceiver with DelegatingStatsReceiver {
     val repr: AnyRef = this
 
+    override def scopeTranslation: NameTranslatingStatsReceiver.Mode =
+      NameTranslatingStatsReceiver.FullTranslation
+
     def counter(metricBuilder: MetricBuilder) =
       BroadcastCounter(srs.map { _.counter(metricBuilder) })