poolmanager: enable staging by default

Motivation:
The default pool manager partition configuration disallows stage.
However, if HSM is connected to dCache, then, probably, we want to make
use of it. Thus, admins should explicitly disallow staging if HSM
connected, but shouldn't be used.

Modification:
Change default value of `stage-allowed` to `yes`.

Result:
more practical default.

Fixes: #7622
Acked-by: Lea Morschel
Acked-by: Karen Hoyos
Acked-by: Dmitry Litvintsev
Target: master
Require-book: no
Require-notes: yes

modules/dcache/src/main/java/org/dcache/poolmanager/Partition.java

@@ -75,7 +75,7 @@ public abstract class Partition implements Serializable {
                 .put("p2p-allowed", "yes")
                 .put("p2p-oncost", "no")
                 .put("p2p-fortransfer", "no")
-                .put("stage-allowed", "no")
+                .put("stage-allowed", "yes")
                 .put("stage-oncost", "no")
                 .build();