Add example for lusture max cached size tuning

examples/kubernetes/max_cache_tuning/README.md

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+## Tuning Lustre Max Memory Cache
+This example shows how to set lustre `llite.*.max_cached_mb` using init container. Lustre client interacts with lustre kernel module for data caching at host level. Since the cache resides in kernel space, it won't be counted toward application container's memory limit. Sometimes it is desireable to reduce the lustre cache size to limit memory consumption at host level. In this example, the max cache size is set to 32MB, but other values may be selected depending on what makes sense for the workload.
+
+### Edit [Pod](./specs/pod.yaml)
+```
+apiVersion: v1
+kind: Pod
+metadata:
+  name: fsx-app
+spec:
+  initContainers:
+  - name: set-lustre-cache
+    image: amazon/aws-fsx-csi-driver:latest
+    securityContext:
+      privileged: true
+    command: ["/sbin/lctl"]
+    args: ["set_param", "llite.*.max_cached_mb=32"]
+  containers:
+  - name: app
+    image: amazonlinux:2
+    command: ["/bin/sh"]
+    args: ["-c", "sleep 999999"]
+    volumeMounts:
+    - name: persistent-storage
+      mountPath: /data
+  volumes:
+  - name: persistent-storage
+    persistentVolumeClaim:
+      claimName: fsx-claim
+```
+The `fsx-app` pod has an init container that sets `llite.*.max_cached_mb` using `lctl`.
+
+## Notes
+* The aws-fsx-csi-driver image is reused in the init container for the `lctl` command. You could chose your own container image for this purpose as long as the lustre client user space tools `lctl` is available inside the image.
+* The init container needs to be privileged as required by `lctl`

examples/kubernetes/max_cache_tuning/specs/claim.yaml

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+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: fsx-claim
+spec:
+  accessModes:
+    - ReadWriteMany
+  storageClassName: fsx-sc
+  resources:
+    requests:
+      storage: 1200Gi

examples/kubernetes/max_cache_tuning/specs/pod.yaml

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+apiVersion: v1
+kind: Pod
+metadata:
+  name: fsx-app
+spec:
+  initContainers:
+  - name: set-lustre-cache
+    image: amazon/aws-fsx-csi-driver:latest
+    securityContext:
+      privileged: true
+    command: ["/sbin/lctl"]
+    args: ["set_param", "llite.*.max_cached_mb=32"]
+  containers:
+  - name: app
+    image: amazonlinux:2
+    command: ["/bin/sh"]
+    args: ["-c", "sleep 999999"]
+    volumeMounts:
+    - name: persistent-storage
+      mountPath: /data
+  volumes:
+  - name: persistent-storage
+    persistentVolumeClaim:
+      claimName: fsx-claim

examples/kubernetes/max_cache_tuning/specs/storageclass.yaml

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+kind: StorageClass
+apiVersion: storage.k8s.io/v1
+metadata:
+  name: fsx-sc
+provisioner: fsx.csi.aws.com
+parameters:
+  subnetId: subnet-0d7b5e117ad7b4961
+  securityGroupIds: sg-05a37bfe01467059a
+mountOptions:
+  - flock