Serialize/unserialize is_pod_sandbox

Instead of inferring is_pod_sandbox from the container name only for
docker, save/load it to json directly from the container info. This
ensures it works for other container engines than docker.

userspace/libsinsp/container.cpp

@@ -147,6 +147,7 @@ string sinsp_container_manager::container_to_json(const sinsp_container_info& co
 	container["imagetag"] = container_info.m_imagetag;
 	container["imagedigest"] = container_info.m_imagedigest;
 	container["privileged"] = container_info.m_privileged;
+	container["is_pod_sandbox"] = container_info.m_is_pod_sandbox;
 
 	Json::Value mounts = Json::arrayValue;
 

userspace/libsinsp/parsers.cpp

@@ -4500,11 +4500,14 @@ void sinsp_parser::parse_container_json_evt(sinsp_evt *evt)
 		if(!name.isNull() && name.isConvertibleTo(Json::stringValue))
 		{
 			container_info.m_name = name.asString();
-			if(container_info.m_type == CT_DOCKER && container_info.m_name.find("k8s_POD") == 0)
-			{
-				container_info.m_is_pod_sandbox = true;
-			}
 		}
+
+		const Json::Value& is_pod_sandbox = container["isPodSandbox"];
+		if(!is_pod_sandbox.isNull() && is_pod_sandbox.isConvertibleTo(Json::booleanValue))
+		{
+			container_info.m_is_pod_sandbox = is_pod_sandbox.asBool();
+		}
+
 		const Json::Value& image = container["image"];
 		if(!image.isNull() && image.isConvertibleTo(Json::stringValue))
 		{