Clear the telemetry cache shm to indicate expiration (#1188)

Signed-off-by: Bob Weinand <[email protected]>

Author: bwoebi

datadog-sidecar/src/service/telemetry.rs

@@ -228,6 +228,12 @@ impl TelemetryCachedClient {
     }
 }
 
+impl Drop for TelemetryCachedClient {
+    fn drop(&mut self) {
+        self.shm_writer.write(&[]);
+    }
+}
+
 type ServiceString = String;
 type EnvString = String;
 type TelemetryCachedClientKey = (ServiceString, EnvString);