skip test_bgp_slb advanced reboot for isolated topo (sonic-net#17470)

What is the motivation for this PR?
'isolated' topology doesn't support warm/fast reboot. skip the test case.

How did you do it?
skip it.

How did you verify/test it?
verified on physical testbed.

Author: sdszhang

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -169,7 +169,7 @@ bgp/test_bgp_slb.py::test_bgp_slb_neighbor_persistence_across_advanced_reboot:
     conditions_logical_operator: or
     conditions:
       - "topo_name in ['dualtor', 'dualtor-56', 'dualtor-120', 'dualtor-aa', 'dualtor-aa-56'] and https://github.com/sonic-net/sonic-mgmt/issues/9201"
-      - "'backend' in topo_name or 'mgmttor' in topo_name"
+      - "'backend' in topo_name or 'mgmttor' in topo_name or 'isolated' in topo_name"
 
 bgp/test_bgp_speaker.py:
   skip: