Fix the issue where the test case randomly fails due to not waiting a…

…fter updating the config DB. (sonic-net#3323)

tests/dvslib/dvs_hash.py

@@ -1,5 +1,6 @@
 """Utilities for interacting with HASH objects when writing VS tests."""
 from typing import Dict, List
+import time
 
 
 class DVSHash:
@@ -21,6 +22,7 @@ def update_switch_hash(
     ) -> None:
         """Update switch hash global in Config DB."""
         self.config_db.update_entry(self.CDB_SWITCH_HASH, self.KEY_SWITCH_HASH_GLOBAL, qualifiers)
+        time.sleep(1)
 
     def get_hash_ids(
         self,

tests/test_dash_acl.py

@@ -87,10 +87,12 @@ def __setitem__(self, key: str, pairs: Union[dict, list, tuple]):
             pairs_str.append((to_string(k), to_string(v)))
         self.table.set(key, pairs_str)
         self.keys.add(key)
+        time.sleep(1)
 
     def __delitem__(self, key: str):
         self.table.delete(str(key))
         self.keys.discard(key)
+        time.sleep(1)
 
     def get_keys(self):
         return self.keys

tests/test_dash_vnet.py

@@ -42,9 +42,11 @@ def __setitem__(self, key: str, pairs: typing.Union[dict, list, tuple]):
         for k, v in pairs:
             pairs_str.append((to_string(k), to_string(v)))
         self.table.set(key, pairs_str)
+        time.sleep(1)
 
     def __delitem__(self, key: str):
         self.table.delete(str(key))
+        time.sleep(1)
 
 
 class Table(object):

tests/test_ipv6_link_local.py

@@ -59,10 +59,10 @@ def test_NeighborAddRemoveIpv6LinkLocal(self, dvs, testlog):
         time.sleep(2)
 
         # Neigh entries should contain Ipv6-link-local neighbors, should be 4
-        neigh_entries = self.pdb.get_keys("NEIGH_TABLE")
-        assert (len(neigh_entries) == 4)
+        self.pdb.wait_for_n_keys("NEIGH_TABLE", 4)
 
         found_entry = False
+        neigh_entries = self.pdb.get_keys("NEIGH_TABLE")
         for key in neigh_entries:
             if (key.find("Ethernet4:2001::2") or key.find("Ethernet0:2000::2")):
                 found_entry = True