Add external-attacher to mock CSI driver deployment

[chrishenzie]

What type of PR is this?
/kind feature

What this PR does / why we need it:
This PR bundles the external-attacher in the mock CSI driver deployment manifest. Including this pod makes it easier for users to quickly test volume attachment / detachment behavior.

Does this PR introduce a user-facing change?:

NONE

/sig storage
/assign @msau42
/assign @Jiawei0227

[Jiawei0227]

/lgtm thanks, Chris!

[msau42]

/approve

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This pull-request has been approved by: chrishenzie, msau42

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[Jiawei0227]

/lgtm

[pohly]

Including this pod makes it easier for users to quickly test volume attachment / detachment behavior.

Do users really deploy the mock driver to test attach/detach? Who are those users and why do they use the mock driver for this?

[chrishenzie]

I'm one of those users. I've been making changes to the CSIAttacher and AttachDetachController and am using this mock driver deployment combined with E2E tests to gather performance metrics when working in kind.

[msau42]

One of the main purposes of mock driver is for Kubernetes developers to test changes to Kubernetes/sidecars. So I think we should be supporting use of all Kubernetes features.

[pohly]

I don't mind adding it, I was just wondering. When I test sidecars, I do it with the hostpath driver, therefore I was wondering why someone would prefer to do it with the mock drivver.