Add isc-dhcp-server to example debootstrap script

Debian 13+ no longer include isc-dhcp-server (or any DHCP client it
seems) in their default minimal stack. This can cause cloud-init to fail
early and render newly provsiioned VMs unbootable. We add it to the
example here for posterity.

api-daemon/provisioner/examples/script/3-debootstrap.py

@@ -485,6 +485,7 @@ class VMBuilderScript(VMBuilder):
                 "acpid",
                 "acpi-support-base",
                 "wget",
+                "isc-dhcp-server",  # required for cloud-init on Debian 13+ where this is no longer standard
             ]
 
         # We need to know our root disk for later GRUB-ing

node-daemon/pvcnoded/dnsmasq-zookeeper-leases.py

@@ -130,6 +130,8 @@ def read_lease_database(zk_conn, zk_leases_key):
 def add_lease(zk_conn, zk_leases_key, expiry, macaddr, ipaddr, hostname, clientid):
     if not hostname:
         hostname = ""
+    try:
+        zk_conn.delete("{}/{}".format(zk_leases_key, macaddr), recursive=True)
         transaction = zk_conn.transaction()
         transaction.create("{}/{}".format(zk_leases_key, macaddr), "".encode("ascii"))
         transaction.create(
@@ -145,6 +147,8 @@ def add_lease(zk_conn, zk_leases_key, expiry, macaddr, ipaddr, hostname, clienti
             "{}/{}/clientid".format(zk_leases_key, macaddr), clientid.encode("ascii")
         )
         transaction.commit()
+    except Exception as e:
+        print(f"FATAL: {e}")
 
 
 def del_lease(zk_conn, zk_leases_key, macaddr, expiry):