media-session: try to load config from state dir first

First try to load conf from the user config directory and then from
the global config dir. Allows users to copy and modify a custom
config file.

src/daemon/media-session.d/alsa-monitor.conf

@@ -1,3 +1,4 @@
+# alsa-monitor config file
 {
   properties = {
   }

src/daemon/media-session.d/media-session.conf

@@ -1,3 +1,4 @@
+# media-session config file
 {
   properties = {
   }