kvm: apply rbd_default_data_pool when creating volumes from templates on RBD

RBD erasure-coded pool support (#9808) added handling of the
rbd_default_data_pool storage-pool detail to RBDStringBuilder (qemu-img
path) and to createPhysicalDisk (blank volumes), but not to
createDiskFromTemplateOnRBD. As a result, ROOT volumes created from a
template via rados-java rbd.clone()/rbd.create() are created without a
data pool: all of their data objects land in the (replicated) metadata
pool instead of the erasure-coded data pool, defeating the point of EC
and consuming ~3x raw space.

Set rbd_default_data_pool on the Rados connection (before connect) in
both the same-cluster clone/copy branch and the cross-cluster copy
branch of createDiskFromTemplateOnRBD, using the destination pool's
detail. librbd then honors it as the default data pool when the new
image is created, so template-derived volumes get data_pool set, the
same way blank volumes already do.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: bradh352

plugins/hypervisors/kvm/src/main/java/com/cloud/hypervisor/kvm/storage/LibvirtStorageAdaptor.java

@@ -1350,6 +1350,8 @@ private KVMPhysicalDisk createDiskFromTemplateOnRBD(KVMPhysicalDisk template,
          */
 
         KVMStoragePool srcPool = template.getPool();
+        Map<String, String> destDetails = destPool.getDetails();
+        String dataPool = (destDetails == null) ? null : destDetails.get(KVMPhysicalDisk.RBD_DEFAULT_DATA_POOL);
         KVMPhysicalDisk disk = null;
         String newUuid = name;
 
@@ -1398,6 +1400,10 @@ private KVMPhysicalDisk createDiskFromTemplateOnRBD(KVMPhysicalDisk template,
                     r.confSet("mon_host", srcPool.getSourceHost() + ":" + srcPool.getSourcePort());
                     r.confSet("key", srcPool.getAuthSecret());
                     r.confSet("client_mount_timeout", "30");
+                    if (dataPool != null) {
+                        logger.debug("Setting RBD data pool to " + dataPool + " for the new image " + disk.getName());
+                        r.confSet(KVMPhysicalDisk.RBD_DEFAULT_DATA_POOL, dataPool);
+                    }
                     r.connect();
                     logger.debug("Successfully connected to Ceph cluster at " + r.confGet("mon_host"));
 
@@ -1476,6 +1482,10 @@ private KVMPhysicalDisk createDiskFromTemplateOnRBD(KVMPhysicalDisk template,
                     rDest.confSet("mon_host", destPool.getSourceHost() + ":" + destPool.getSourcePort());
                     rDest.confSet("key", destPool.getAuthSecret());
                     rDest.confSet("client_mount_timeout", "30");
+                    if (dataPool != null) {
+                        logger.debug("Setting RBD data pool to " + dataPool + " on the destination cluster for the new image " + disk.getName());
+                        rDest.confSet(KVMPhysicalDisk.RBD_DEFAULT_DATA_POOL, dataPool);
+                    }
                     rDest.connect();
                     logger.debug("Successfully connected to source Ceph cluster at " + rDest.confGet("mon_host"));