add healthy check for pfcwd wb (sonic-net#14320)

What is the motivation for this PR?
The case is flaky, failed sometimes.

How did you do it?
Add healthy check after warm reboot to determine whether the failed caused by warm-reboot or pfcwd

How did you verify/test it?
Local run the case

tests/pfcwd/test_pfcwd_warm_reboot.py

@@ -19,6 +19,7 @@
 from .files.pfcwd_helper import EXPECT_PFC_WD_DETECT_RE, EXPECT_PFC_WD_RESTORE_RE
 from .files.pfcwd_helper import send_background_traffic
 from .files.pfcwd_helper import has_neighbor_device
+from tests.common.utilities import wait_until
 
 TEMPLATES_DIR = os.path.join(os.path.dirname(os.path.realpath(__file__)), "templates")
 TESTCASE_INFO = {'no_storm': {'test_sequence': ["detect", "restore", "warm-reboot", "detect", "restore"],
@@ -520,8 +521,13 @@ def pfcwd_wb_helper(self, fake_storm, testcase_actions, setup_pfc_test, enum_fan
         self.storm_threads = []
 
         for t_idx, test_action in enumerate(testcase_actions):
+            logger.info("Index {} test_action {}".format(t_idx, test_action))
             if 'warm-reboot' in test_action:
                 reboot(self.dut, localhost, reboot_type="warm", wait_warmboot_finalizer=True)
+
+                assert wait_until(300, 20, 20, self.dut.critical_services_fully_started), \
+                    "All critical services should fully started!"
+
                 continue
 
             # Need to wait some time after warm-reboot for the counters to be created