alsa: fix build warnings

Fix build warnings introduced by commit 2f0eaa68.

Change-Id: I290e1bc38086efe1036ad0146b89030db9de0a0c
Tuleap: #171

src/media/audio/alsa/alsalayer.cpp

@@ -52,7 +52,7 @@ private:
 };
 
 AlsaThread::AlsaThread(AlsaLayer *alsa)
-    : thread_(), alsa_(alsa), running_(false)
+    : alsa_(alsa), running_(false), thread_()
 {}
 
 bool AlsaThread::isRunning() const