Update telemetry docker entry flow to detect FEATURE table (#23756)

keep FEATURE controlling the container functioning or not, but do not want container to be rollouted/rollbacked via k8s during FEATURE switch changes, thus have container check  FEATURE table itself and stay idling if FEATURE is disabled

Author: FengPan-Frank

dockers/docker-sonic-telemetry/Dockerfile.j2

@@ -26,6 +26,7 @@ COPY ["start.sh", "telemetry.sh", "dialout.sh", "/usr/bin/"]
 COPY ["telemetry_vars.j2", "/usr/share/sonic/templates/"]
 COPY ["supervisord.conf", "/etc/supervisor/conf.d/"]
 COPY ["critical_processes", "/etc/supervisor"]
+COPY ["docker-telemetry-entry.sh", "/usr/local/bin/"]
 
 FROM $BASE
 
@@ -37,4 +38,5 @@ ENV DEBIAN_FRONTEND=noninteractive
 # Pass the image_version to container
 ENV IMAGE_VERSION=$image_version
 
-ENTRYPOINT ["/usr/local/bin/supervisord"]
+RUN chmod +x /usr/local/bin/docker-telemetry-entry.sh
+ENTRYPOINT ["/usr/local/bin/docker-telemetry-entry.sh"]

dockers/docker-sonic-telemetry/docker-telemetry-entry.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+while true; do
+  STATE=$(redis-cli -n 4 HGET "FEATURE|telemetry" state)
+  if [ "$STATE" == "enabled" ]; then
+    echo "Telemetry is enabled. Starting service..."
+    break
+  else
+    echo "Telemetry is disabled. Entering idle..."
+    sleep 10
+  fi
+done
+
+exec /usr/local/bin/supervisord