feat: add fixture for disabling route check (sonic-net#16876)

Description of PR
Add a module-level fixture for temporarily disabling route check for a test module

Summary:
Fixes # (issue) Microsoft ADO 31326413

Approach
What is the motivation for this PR?
In our recent Cisco T2 Nightly run, we observed that we would get the following error syslog during some test modules:

E               Failed: Processes "['analyze_logs--<MultiAsicSonicHost dut-lc1-1>']" failed with exit code "1"
E               Exception:
E               match: 1
E               expected_match: 0
E               expected_missing_match: 0
E               
E               Match Messages:
E               2025 Feb  3 03:03:29.550827 svcstr2-8800-lc1-1 ERR monit[914]: 'routeCheck' status failed (255) -- Failure results: {{sonic-net#12    "asic1": {sonic-net#12        "Unaccounted_ROUTE_ENTRY_TABLE_entries": [sonic-net#12            "100.1.0.22/32",sonic-net#12
After discussion, we decided to add a fixture so users can disable route check for a test module if they think that test tends to have such error syslog.

How did you do it?
How did you verify/test it?
I ran the updated code and can confirm it's working well.

co-authorized by: [email protected]

Author: cyw233

tests/conftest.py

@@ -2616,6 +2616,41 @@ def _remove_entry(table_name, key_name, config):
             add_custom_msg(request, f"{DUT_CHECK_NAMESPACE}.config_db_check_failed", config_db_check_failed)
 
 
+@pytest.fixture(scope="module", autouse=True)
+def temporarily_disable_route_check(request, duthosts):
+    check_flag = False
+    for m in request.node.iter_markers():
+        if m.name == "disable_route_check":
+            check_flag = True
+            break
+
+    def run_route_check(dut):
+        rc = dut.shell("sudo route_check.py", module_ignore_errors=True)
+        if rc['rc'] != 0:
+            pytest.fail("route_check.py failed on DUT {} in test setup/teardown stage".format(dut.hostname))
+
+    if check_flag:
+        with SafeThreadPoolExecutor(max_workers=8) as executor:
+            for duthost in duthosts.frontend_nodes:
+                executor.submit(run_route_check, duthost)
+
+        with SafeThreadPoolExecutor(max_workers=8) as executor:
+            for duthost in duthosts.frontend_nodes:
+                executor.submit(duthost.shell, "sudo monit stop routeCheck")
+
+    yield
+
+    if check_flag:
+        try:
+            with SafeThreadPoolExecutor(max_workers=8) as executor:
+                for duthost in duthosts.frontend_nodes:
+                    executor.submit(run_route_check, duthost)
+        finally:
+            with SafeThreadPoolExecutor(max_workers=8) as executor:
+                for duthost in duthosts.frontend_nodes:
+                    executor.submit(duthost.shell, "sudo monit start routeCheck")
+
+
 @pytest.fixture(scope="function")
 def on_exit():
     '''

tests/platform_tests/link_flap/test_cont_link_flap.py

@@ -23,6 +23,7 @@
 from tests.common.platform.device_utils import toggle_one_link
 
 pytestmark = [
+    pytest.mark.disable_route_check,
     pytest.mark.disable_loganalyzer,
     pytest.mark.topology('any')
 ]