Adding node without dc leads to broken `cassandra-rackdc.properties`

[dkropachev]

Steps:

ccm create --scylla -n 1:0 -i 127.0.0. -v release:2025.1 -b test-ccm-bug
ccm start --wait-other-notice --wait-for-binary-proto --jvm_arg=--skip-wait-for-gossip-to-settle=0
ccm add -b -i 127.0.0.2 -j 7200 -r 2200 --scylla node2
ccm node2 start --wait-other-notice --wait-for-binary-proto --jvm_arg=--skip-wait-for-gossip-to-settle=0

Ends up at error:

Traceback (most recent call last):
  File "~/.venv/bin/ccm", line 74, in <module>
    cmd.run()
  File "~/.venv/lib/python3.11/site-packages/ccmlib/cmds/node_cmds.py", line 196, in run
    self.node.start(not self.options.no_join_ring,
  File "~/scylla-ccm/.venv/lib/python3.11/site-packages/ccmlib/scylla_node.py", line 762, in start
    scylla_process = self._start_scylla(args=args, marks=marks, update_pid=update_pid,
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "~/.venv/lib/python3.11/site-packages/ccmlib/scylla_node.py", line 405, in _start_scylla
    self.wait_for_binary_interface(from_mark=from_mark, process=self._process_scylla, timeout=t)
  File "~/.venv/lib/python3.11/site-packages/ccmlib/node.py", line 546, in wait_for_binary_interface
    self.watch_log_for("Starting listening for CQL clients", **kwargs)
  File "~/.venv/lib/python3.11/site-packages/ccmlib/node.py", line 512, in watch_log_for
    raise RuntimeError(f"The process is dead, returncode={process.returncode}")
RuntimeError: The process is dead, returncode=1

Node2 start fails with:

ERROR 2025-04-17 08:59:28,804 [shard 0:main] snitch_logger - Property file ~/.ccm/cpp-driver_2025-1-0_1-0/node2/conf/cassandra-rackdc.properties is incomplete. Some obligatory fields are missing.
ERROR 2025-04-17 08:59:28,804 [shard 0:main] snitch_logger - Failed to parse a properties file (~/.ccm/cpp-driver_2025-1-0_1-0/node2/conf/cassandra-rackdc.properties). Halting...
ERROR 2025-04-17 08:59:28,805 [shard 0:main] init - Startup failed: locator::bad_property_file_error (std::exception)