{RDBMS} az postgres flexible-server restore: fix cross-subscription restore issue

Author: Matthew Boentoro

src/azure-cli/azure/cli/command_modules/rdbms/flexible_server_custom_postgres.py

@@ -233,12 +233,10 @@ def flexible_server_restore(cmd, client,
             logging_name='PostgreSQL', command_group='postgres', server_client=client, location=location)
         validate_server_name(db_context, server_name, 'Microsoft.DBforPostgreSQL/flexibleServers')
 
-        instance = client.get(id_parts['resource_group'], id_parts['name'])
-
-        cluster_byok_validator(byok_identity, byok_key, backup_byok_identity, backup_byok_key, geo_redundant_backup, instance)
+        cluster_byok_validator(byok_identity, byok_key, backup_byok_identity, backup_byok_key, geo_redundant_backup, source_server_object)
         pg_byok_validator(byok_identity, byok_key, backup_byok_identity, backup_byok_key, geo_redundant_backup)
 
-        storage = postgresql_flexibleservers.models.Storage(type=storage_type if instance.storage.type != "PremiumV2_LRS" else None)
+        storage = postgresql_flexibleservers.models.Storage(type=storage_type if source_server_object.storage.type != "PremiumV2_LRS" else None)
 
         parameters = postgresql_flexibleservers.models.Server(
             location=location,