[config]Restrict YANG validation to Golden Config (#3656)

What I did
The sonic vm image has yang validation issue with default config setup. Limit YANG check to golden config only before fix default factory config.

How I did it
Restrict YANG validation to golden config only.

How to verify it
Unit test and integration test.

Author: wen587

config/main.py

@@ -1830,7 +1830,7 @@ def reload(db, filename, yes, load_sysinfo, no_service_restart, force, file_form
         if multi_asic.is_multi_asic():
             # Multiasic has not 100% fully validated. Thus pass here.
             pass
-        else:
+        elif "golden" in filename.lower():
             config_file_yang_validation(filename)
 
     #Stop services before config push

tests/config_test.py

@@ -1231,6 +1231,7 @@ def teardown_class(cls):
 
 class TestReloadConfig(object):
     dummy_cfg_file = os.path.join(os.sep, "tmp", "config.json")
+    dummy_golden_cfg_file = os.path.join(os.sep, "tmp", "golden_config.json")
 
     @classmethod
     def setup_class(cls):
@@ -1433,7 +1434,7 @@ def test_reload_yang_config(self, get_cmd_module,
                 == RELOAD_YANG_CFG_OUTPUT.format(config.SYSTEM_RELOAD_LOCK)
 
     def test_reload_config_fails_yang_validation(self, get_cmd_module, setup_single_broadcom_asic):
-        with open(self.dummy_cfg_file, 'w') as f:
+        with open(self.dummy_golden_cfg_file, 'w') as f:
             device_metadata = {
                 "DEVICE_METADATA": {
                     "localhost": {
@@ -1452,7 +1453,7 @@ def test_reload_config_fails_yang_validation(self, get_cmd_module, setup_single_
 
             result = runner.invoke(
                 config.config.commands["reload"],
-                [self.dummy_cfg_file, '-y', '-f'])
+                [self.dummy_golden_cfg_file, '-y', '-f'])
 
             print(result.exit_code)
             print(result.output)
@@ -1464,6 +1465,7 @@ def test_reload_config_fails_yang_validation(self, get_cmd_module, setup_single_
     def teardown_class(cls):
         os.environ['UTILITIES_UNIT_TESTING'] = "0"
         os.remove(cls.dummy_cfg_file)
+        os.remove(cls.dummy_golden_cfg_file)
         print("TEARDOWN")