Add drop cache when change nodes state

Current iptables fixture tears down nodes in order modify iptables.
When the machines started again the cached info must be
refreshed.

In case machines state changed like stop/reboot cashed info may
hide bugs in the node controllers or fail tests.

src/tests/base_test.py

@@ -644,7 +644,8 @@ def set_iptables_rules_for_nodes(
             for node in given_nodes:
                 given_node_ips.append(node.ips[0])
             cluster.nodes.shutdown_given(given_nodes)
-
+            # Clear cached info about nodes after shutdown
+            cluster.nodes.drop_cache()
             log.info(f"Given node ips: {given_node_ips}")
 
             for _rule in iptables_rules: