Merge pull request #8285 from gyuho/news

NEWS: add v3.2.4

NEWS

@@ -1,3 +1,7 @@
+etcd v3.2.4 (2017-07-19)
+- do not block on active client stream when stopping server
+- fix gRPC proxy Snapshot RPC error handling
+
 etcd v3.2.3 (2017-07-14)
 - let clients establish unlimited streams
 - add docker tags for minor versions