TelematicPlugin: Memory leak (#599)

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# PR Details
## Description
Fix memory leaks issues with several variables created with malloc or
new.
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## Related Issue
#575
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## Motivation and Context

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## How Has This Been Tested?
Local integration test
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## Types of changes

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- [x] Defect fix (non-breaking change that fixes an issue)
- [ ] New feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that cause existing functionality
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## Checklist:

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- [ ] I have added any new packages to the sonar-scanner.properties file
- [ ] My change requires a change to the documentation.
- [ ] I have updated the documentation accordingly.
- [x] I have read the **CONTRIBUTING** document.
[V2XHUB Contributing
Guide](https://github.com/usdot-fhwa-OPS/V2X-Hub/blob/develop/Contributing.md)
- [ ] I have added tests to cover my changes.
- [ ] All new and existing tests passed.

src/v2i-hub/TelematicBridgePlugin/src/TelematicBridgeMsgWorker.h

@@ -147,7 +147,9 @@ namespace TelematicBridge
         {
             throw TelematicBridgeException("Failed to  convert message with ID (=" + to_string(messageFrame->messageId) + ") to XML ");
         }
-        return string(xml_buffer.buffer);
+        auto output = string(xml_buffer.buffer);
+        FREEMEM(xml_buffer.buffer);
+        return output;
     }
 
     /**
@@ -238,7 +240,10 @@ namespace TelematicBridge
             }
             else
             {
-                json["payload"] = StringToJson(cJSON_Print(msg->payload));
+                // Render a cJSON entity to text for transfer/storage. Free the char* when finished.
+                auto payloadPtr = cJSON_Print(msg->payload);    
+                json["payload"] = StringToJson(payloadPtr);
+                FREEMEM(payloadPtr);
             }
         }