Update RPM spec (use git version when it is possible)

[linphone] / mediastreamer2

diff --git a/mediastreamer2 b/mediastreamer2
index 513945c9781dbb9ae6905bb7fa80db2665f64d01..9d722a1456c8574b385fac0eadf4ad6a4067637b 160000 (submodule)
--- a/mediastreamer2
+++ b/mediastreamer2
@@ -1 +1 @@
-Subproject commit 513945c9781dbb9ae6905bb7fa80db2665f64d01
+Subproject commit 9d722a1456c8574b385fac0eadf4ad6a4067637b