Update ms2 for upnp improvement

[linphone] / mediastreamer2

diff --git a/mediastreamer2 b/mediastreamer2
index 710c3da85157d4db17bfce21e7d2b7853377fa4e..b21f304297319e15fbe0beb3509592022eb8e88a 160000 (submodule)
--- a/mediastreamer2
+++ b/mediastreamer2
@@ -1 +1 @@
-Subproject commit 710c3da85157d4db17bfce21e7d2b7853377fa4e
+Subproject commit b21f304297319e15fbe0beb3509592022eb8e88a