Make advance_version_for_expected_database available for other db migrator test cases as well (sonic-net#1614)

- What I did
Originally, the method advance_version_for_expected_database was introduced (in sonic-net#1566) to handle the case the latest version in CONFIG_DB is greater than the latest version in mellanox_buffer_migrator.
Now there are other database migrators whose test cases can also encounter this situation, like port auto-negotiation (sonic-net#1568) and port-channel for LACP key (sonic-net#1473).
So I would like to make the method public, available for all database migrators.
Related database migrator test cases have been updated accordingly.

- How to verify it
Run the unit test.

Signed-off-by: Stephen Sun <stephens@nvidia.com>

Author: stephenxs

tests/db_migrator_input/config_db/non-default-config-expected.json

@@ -1115,6 +1115,6 @@
         "speed": "50000"
     },
     "VERSIONS|DATABASE": {
-        "VERSION": "version_2_0_1"
+        "VERSION": "version_2_0_0"
     }
 }

tests/db_migrator_test.py

@@ -24,6 +24,17 @@ def get_sonic_version_info_mlnx():
     return {'asic_type': 'mellanox'}
 
 
+def advance_version_for_expected_database(migrated_db, expected_db, last_interested_version):
+    # In case there are new db versions greater than the latest one that mellanox buffer migrator is interested,
+    # we just advance the database version in the expected database to make the test pass
+    expected_dbversion = expected_db.get_entry('VERSIONS', 'DATABASE')
+    dbmgtr_dbversion = migrated_db.get_entry('VERSIONS', 'DATABASE')
+    if expected_dbversion and dbmgtr_dbversion:
+        if expected_dbversion['VERSION'] == last_interested_version and dbmgtr_dbversion['VERSION'] > expected_dbversion['VERSION']:
+            expected_dbversion['VERSION'] = dbmgtr_dbversion['VERSION']
+            expected_db.set_entry('VERSIONS', 'DATABASE', expected_dbversion)
+
+
 class TestMellanoxBufferMigrator(object):
     @classmethod
     def setup_class(cls):
@@ -76,16 +87,6 @@ def check_appl_db(self, result, expected):
             for key in keys:
                 assert expected.get_all(expected.APPL_DB, key) == result.get_all(result.APPL_DB, key)
 
-    def advance_version_for_expected_database(self, migrated_db, expected_db):
-        # In case there are new db versions greater than the latest one that mellanox buffer migrator is interested,
-        # we just advance the database version in the expected database to make the test pass
-        expected_dbversion = expected_db.get_entry('VERSIONS', 'DATABASE')
-        dbmgtr_dbversion = migrated_db.get_entry('VERSIONS', 'DATABASE')
-        if expected_dbversion and dbmgtr_dbversion:
-            if expected_dbversion['VERSION'] == self.version_list[-1] and dbmgtr_dbversion['VERSION'] > expected_dbversion['VERSION']:
-                expected_dbversion['VERSION'] = dbmgtr_dbversion['VERSION']
-                expected_db.set_entry('VERSIONS', 'DATABASE', expected_dbversion)
-
     @pytest.mark.parametrize('scenario',
                              ['empty-config',
                               'non-default-config',
@@ -103,7 +104,7 @@ def test_mellanox_buffer_migrator_negative_cold_reboot(self, scenario):
         dbmgtr = db_migrator.DBMigrator(None)
         dbmgtr.migrate()
         expected_db = self.mock_dedicated_config_db(db_after_migrate)
-        self.advance_version_for_expected_database(dbmgtr.configDB, expected_db.cfgdb)
+        advance_version_for_expected_database(dbmgtr.configDB, expected_db.cfgdb, self.version_list[-1])
         self.check_config_db(dbmgtr.configDB, expected_db.cfgdb)
         assert not dbmgtr.mellanox_buffer_migrator.is_buffer_config_default
 
@@ -142,7 +143,7 @@ def test_mellanox_buffer_migrator_for_cold_reboot(self, sku_version, topo):
 
             # Eventually, the config db should be migrated to the latest version
             expected_db = self.mock_dedicated_config_db(self.make_db_name_by_sku_topo_version(sku, topo, self.version_list[-1]))
-            self.advance_version_for_expected_database(dbmgtr.configDB, expected_db.cfgdb)
+            advance_version_for_expected_database(dbmgtr.configDB, expected_db.cfgdb, self.version_list[-1])
             self.check_config_db(dbmgtr.configDB, expected_db.cfgdb)
             assert dbmgtr.mellanox_buffer_migrator.is_buffer_config_default
 
@@ -158,7 +159,7 @@ def mellanox_buffer_migrator_warm_reboot_runner(self, input_config_db, input_app
         import db_migrator
         dbmgtr = db_migrator.DBMigrator(None)
         dbmgtr.migrate()
-        self.advance_version_for_expected_database(dbmgtr.configDB, expected_config_db.cfgdb)
+        advance_version_for_expected_database(dbmgtr.configDB, expected_config_db.cfgdb, self.version_list[-1])
         assert dbmgtr.mellanox_buffer_migrator.is_buffer_config_default == is_buffer_config_default_expected
         self.check_config_db(dbmgtr.configDB, expected_config_db.cfgdb)
         self.check_appl_db(dbmgtr.appDB, expected_appl_db)
@@ -210,8 +211,10 @@ def test_port_autoneg_migrator(self):
         import db_migrator
         dbmgtr = db_migrator.DBMigrator(None)
         dbmgtr.migrate()
+
         dbconnector.dedicated_dbs['CONFIG_DB'] = os.path.join(mock_db_path, 'config_db', 'port-an-expected')
         expected_db = Db()
+        advance_version_for_expected_database(dbmgtr.configDB, expected_db.cfgdb, 'version_2_0_1')
 
         assert dbmgtr.configDB.get_table('PORT') == expected_db.cfgdb.get_table('PORT')
         assert dbmgtr.configDB.get_table('VERSIONS') == expected_db.cfgdb.get_table('VERSIONS')