media-session: add option to configure suspend timeout

Set the property on the node and use the value when suspending the
node. a timeout of 0 disables suspend.

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

@@ -60,6 +60,7 @@ rules = [
                 #resample.quality     = 4
                 #channelmix.normalize = false
                 #channelmix.mix-lfe   = false
+                #session.suspend-timeout-seconds = 5      # 0 disables suspend
             }
         }
     }