Fix image name for example webhook, and other nitpicks

[bswartz]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
The image name for the webhook was wrong in the example.
Also fixed a few nitpicks

Does this PR introduce a user-facing change?:

NONE

[xing-yang]

Can you also update the images under external-snapshotter/deploy?
Images should be updated to the following:

k8s.gcr.io/sig-storage/snapshot-controller:v3.0.0
k8s.gcr.io/sig-storage/csi-snapshotter:v3.0.0

[xing-yang]

We should update this one too:

https://github.com/kubernetes-csi/external-snapshotter/blob/master/deploy/kubernetes/csi-snapshotter/setup-csi-snapshotter.yaml#L75
New image:
k8s.gcr.io/sig-storage/csi-provisioner:v2.0.2

We also need to update the hostpath driver when the new image is cut:
https://github.com/kubernetes-csi/external-snapshotter/blob/master/deploy/kubernetes/csi-snapshotter/setup-csi-snapshotter.yaml#L100

[msau42]

@xing-yang longer term, do you see a way to consolidate all these image examples so we don't have to remember to update all these places every time we cut new releases? I am thinking things like making the image version templatable and using git tags or something to get the latest released version.

[bswartz]

/retest

[xing-yang]

/lgtm
/approve

[k8s-ci-robot]

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