Use udev to restore ALSA volume settings

Alsa-utils provides a udev rule to restore volume settings, so use
that instead of restoring them from a systemd service.  The
"alsa-store" service saves the settings on shutdown.

modules/services/audio/alsa.nix

@@ -45,29 +45,19 @@ in
 
     environment.systemPackages = [ alsaUtils ];
 
-    boot.kernelModules = optional config.sound.enableOSSEmulation "snd_pcm_oss";
-
-    jobs.alsa =
-      { description = "ALSA Volume Settings";
-
-        startOn = "stopped udevtrigger";
+    # ALSA provides a udev rule for restoring volume settings.
+    services.udev.packages = [ alsaUtils ];
 
-        preStart =
-          ''
-            mkdir -m 0755 -p $(dirname ${soundState})
-
-            # Try to restore the sound state.
-            ${alsaUtils}/sbin/alsactl --ignore init || true
-            ${alsaUtils}/sbin/alsactl --ignore -f ${soundState} restore || true
-          '';
+    boot.kernelModules = optional config.sound.enableOSSEmulation "snd_pcm_oss";
 
-        postStop =
-          ''
-            # Save the sound state.
-            ${alsaUtils}/sbin/alsactl --ignore -f ${soundState} store
-          '';
+    boot.systemd.services."alsa-store" =
+      { description = "Store Sound Card State";
+        wantedBy = [ "shutdown.target" ];
+        before = [ "shutdown.target" ];
+        unitConfig.DefaultDependencies = "no";
+        serviceConfig.Type = "oneshot";
+        serviceConfig.ExecStart = "${alsaUtils}/sbin/alsactl store --ignore";
       };
-
   };
 
 }