xfail decap related cases for 202412 (#22831)

Description of PR
Summary:
subnet decap tunnel is disabled on 202412 in Azure/sonic-swss.msft#209. xfail related cases.

qos/test_qos_dscp_mapping.py::TestQoSSaiDSCPQueueMapping_IPIP_Base::test_dscp_to_queue_mapping[uniform]
srv6/test_srv6_dataplane:py::TestSRv6DataPlaneBase::test_srv6_full_func

Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com>

---------

Signed-off-by: Dashuai Zhang <dashuaizhang@microsoft.com>

Author: sdszhang

tests/common/plugins/conditional_mark/tests_mark_conditions.yaml

@@ -3954,9 +3954,11 @@ qos/test_qos_dscp_mapping.py::TestQoSSaiDSCPQueueMapping_IPIP_Base::test_dscp_to
       - "'dualtor' in topo_name and asic_type in ['mellanox']"
       - "asic_type in ['marvell-teralynx']"
   xfail:
-    reason: "Test case has issue on the t0-isolated-d256u256s2 topo."
+    reason: "Test case has issue on the 202412 branch as decap tunnel is disabled."
+    conditions_logical_operator: or
     conditions:
       - "'t0-isolated-d256u256s2' in topo_name and platform in ['x86_64-nvidia_sn5640-r0']"
+      - "'isolated' in topo_name and release in ['202412']"
 
 qos/test_qos_masic.py:
   skip:
@@ -4735,6 +4737,12 @@ srv6/test_srv6_dataplane.py:
     conditions:
       - "'t0-isolated-d256u256s2' in topo_name and platform in ['x86_64-nvidia_sn5640-r0']"
 
+srv6/test_srv6_dataplane.py::TestSRv6DataPlaneBase::test_srv6_full_func:
+  xfail:
+    reason: "vlan decap is disabled in 202412 image, which causes the test case failure."
+    conditions:
+      - "'isolated' in topo_name and release in ['202412']"
+
 srv6/test_srv6_static_config.py:
   skip:
     reason: "Requires particular image support, skip in PR testing. Skip for non Arista-7060X6-64PE-B-* TH5 SKUs. Skip for t0-isolated-d96u32, t1-isolated-d32/128"