[config db] Trim garbage charactor in "DEVICE_METADATA" of config db (#3748)

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This is to prevent a user error in ADO: 28004860
where there was an extra "\n" at the end of mac, in "DEVICE_METADATA" section.

![image](https://github.com/sonic-net/sonic-utilities/assets/91497961/41e634d4-1ae0-48bc-9824-72915d10dc25)

#### What I did
1. the garbage char could be generated with "load_minigraph" if '-override-config' is specified, and if golden_config has garbage char.
2. it could also be introduced by "config reload"
#### How I did it
in both cases, add the strip method for "mac" as well as "platform" whenever the DEVICE_METADATA tends to be modified. to trim the extra "\n"
#### How to verify it
1. add an extra "\n" at end of mac, in config db
2. did config reload, garbage char exists
3. apply changes in this PR
#### Previous command output (if the output of a command-line utility has changed)

#### New command output (if the output of a command-line utility has changed)

Author: mssonicbld

config/main.py

@@ -2174,8 +2174,8 @@ def generate_sysinfo(cur_config, config_input, ns=None):
     if not platform:
         platform = device_info.get_platform()
 
-    device_metadata['localhost']['mac'] = mac
-    device_metadata['localhost']['platform'] = platform
+    device_metadata['localhost']['mac'] = mac.rstrip('\n')
+    device_metadata['localhost']['platform'] = platform.rstrip('\n')
 
     return
 

tests/config_override_test.py

@@ -386,10 +386,10 @@ def read_json_file_side_effect(filename):
 
         with mock.patch('config.main.read_json_file',
                         mock.MagicMock(side_effect=read_json_file_side_effect)),\
-                mock.patch('sonic_py_common.device_info.get_platform',
+             mock.patch('sonic_py_common.device_info.get_platform',
                         return_value="multi_asic"),\
-                mock.patch('sonic_py_common.device_info.get_system_mac',
-                        return_value="11:22:33:44:55:66"):
+             mock.patch('sonic_py_common.device_info.get_system_mac',
+                        return_value="11:22:33:44:55:66\n"):
             runner = CliRunner()
             result = runner.invoke(config.config.commands["override-config-table"],
                                    ['golden_config_db.json'], obj=db)