[dvs] Stabilize sub-port tests (sonic-net#1254)

Signed-off-by: Danny Allen <daall@microsoft.com>

Author: daall

tests/dvslib/dvs_database.py

@@ -131,12 +131,8 @@ def wait_for_field_match(self,
             at `key` in the specified table. This method will wait for the
             fields to exist.
 
-            NOTE: We suggest you only use this function if:
-                1) the entry already exists, and
-                2) you expect certain fields to change
-
-            Otherwise, it is more efficient to use `wait_for_entry` and check
-            for the expected fields after the entry has been retrieved.
+            Note:
+                This method does not check for an exact match.
 
             Args:
                 table_name (str): The name of the table where the entry is
@@ -154,7 +150,7 @@ def wait_for_field_match(self,
 
         def _access_function():
             fv_pairs = self.get_entry(table_name, key)
-            return (expected_fields.items() <= fv_pairs.items(), fv_pairs)
+            return (all(fv_pairs.get(k) == v for k, v in expected_fields.items()), fv_pairs)
 
         return wait_for_result(_access_function, polling_config)
 
@@ -208,3 +204,57 @@ def _access_function():
             return (len(keys) == num_keys, keys)
 
         return wait_for_result(_access_function, polling_config)
+
+    def wait_for_matching_keys(self,
+                               table_name,
+                               expected_keys,
+                               polling_config=DEFAULT_POLLING_CONFIG):
+        """
+            Checks if the specified keys exist in the table. This method
+            will wait for the keys to exist.
+
+            Args:
+                table_name (str): The name of the table from which to fetch
+                    the keys.
+                expected_keys (List[str]): The keys we expect to see in the
+                    table.
+                polling_config (PollingConfig): The parameters to use to poll
+                    the db.
+
+            Returns:
+                List[str]: The keys stored in the table. If no keys are found,
+                then an empty List will be returned.
+        """
+
+        def _access_function():
+            keys = self.get_keys(table_name)
+            return (all(key in keys for key in expected_keys), keys)
+
+        return wait_for_result(_access_function, polling_config)
+
+    def wait_for_deleted_keys(self,
+                              table_name,
+                              deleted_keys,
+                              polling_config=DEFAULT_POLLING_CONFIG):
+        """
+            Checks if the specified keys no longer exist in the table. This
+            method will wait for the keys to be deleted.
+
+            Args:
+                table_name (str): The name of the table from which to fetch
+                    the keys.
+                deleted_keys (List[str]): The keys we expect to be removed from
+                    the table.
+                polling_config (PollingConfig): The parameters to use to poll
+                    the db.
+
+            Returns:
+                List[str]: The keys stored in the table. If no keys are found,
+                then an empty List will be returned.
+        """
+
+        def _access_function():
+            keys = self.get_keys(table_name)
+            return (all(key not in keys for key in deleted_keys), keys)
+
+        return wait_for_result(_access_function, polling_config)