jack: use node.lock-quantum by default

As soon as a JACK app is started, the automatic quantum change is
disabled. This means no pulse/alsa app can change the quantum.

The only way to change the quantum is with node.force-quantum or
with the settings metadata.

This means only a JACK buffersize change (usually controlled from the
JACK app, such as in ardour) or a metadata change (from the command
line) can modify things. Both of those are usually caused by a user
action.

For JACK apps where the quantum is allowed to change automatically,
explicit rules need to be placed in the config.

src/daemon/jack.conf.in

@@ -65,7 +65,10 @@ context.modules = [
 # global properties for all jack clients
 jack.properties = {
      #node.latency       = 1024/48000
-     #node.lock-quantum  = false
+     #node.rate          = 1/48000
+     #node.quantum       = 1024/48000
+     #node.lock-quantum  = true
+     #node.force-quantum = 0
      #jack.show-monitor  = true
      #jack.merge-monitor = false
      #jack.short-name    = false