chore(env): Adding required env inside chaosengine (#479)

Signed-off-by: shubhamchaudhary <shubham@chaosnative.com>

charts/generic/pod-memory-hog/experiment.yaml

@@ -86,8 +86,11 @@ spec:
       - name: STRESS_IMAGE
         value: 'alexeiled/stress-ng:latest-ubuntu'
 
+      ## provide the cluster runtime
+      - name: CONTAINER_RUNTIME
+        value: 'docker'   
+
       # provide the socket file path
-      # it is used in pumba lib
       - name: SOCKET_PATH
         value: '/var/run/docker.sock'