tests: fixed querying for the node in decommission test

In current redpanda version node ids are dynamically assigned we can not
use a node id as an index in the `RedpandaService` nodes list as it may
result in incorrect results. In this particular example a node that was
stopped was not the one that was decommissioned, leading to some of the
rf=1 partitions being not available which prevented test from finishing.

Fixes: redpanda-data#11751

Signed-off-by: Michal Maslanka <[email protected]>

tests/rptest/tests/nodes_decommissioning_test.py

@@ -403,7 +403,7 @@ def test_decommissioning_cancel_ongoing_movements(self):
 
         self._wait_for_node_removed(to_decommission)
         # stop decommissioned node
-        self.redpanda.stop_node(self.redpanda.get_node(to_decommission))
+        self.redpanda.stop_node(self.redpanda.get_node_by_id(to_decommission))
 
         self.verify()