drone/ContainerImageDocker: replaced fixed wait time with ready-check loop

drone/ContainerImageDocker.yml

@@ -40,7 +40,6 @@
     MERGE_REGISTRY_JSON: "true"
     DEBUG_STEP: "false"
     PUSH_TAGS: "true"
-    DOCKER_WAIT_START_SECONDS: "5"
 
   commands:
     - &ContainerImageDockerCommands |
@@ -190,8 +189,12 @@
         env
       fi
 
-      # give docker enough time to start
+      # Wait until Docker daemon is running and has completed initialisation
-      sleep $DOCKER_WAIT_START_SECONDS
+      while (! docker stats --no-stream >/dev/null 2>&1); do
+        # Docker takes a few seconds to initialize
+        echo "Waiting for Docker to launch..."
+        sleep 2
+      done
 
       # start build
       echo $ALL_ARGS | xargs docker build