Validate VolumeCapability matches with existing volume in Publish/Stage calls

[davidz627]

We do static validation of volume capability now. However, if an existing volume is found we must validate that the volume capabilities of the existing volume match with the requested capabilities, otherwise we must return an "ALREADY_EXIST" error

[fejta-bot]

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/lifecycle stale

[fejta-bot]

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/lifecycle rotten

[davidz627]

/remove-lifecycle rotten
/lifecycle frozen

[davidz627]

For Publish and Stage we must validate that the VolumeCapability matches whether the volume is block or fs, then if fs that the actual fstype matches.

If requested VolumeCapability is block I don't think we can do any extra validation since a user could format their own fs onto the device and it technically is still block

[saad-ali]

Removing this issue from GA blockers since the current behavior here is the same as the old in-tree behavior:

https://github.com/kubernetes/kubernetes/blob/aec30be5b3341d0937dc12e1d973cacb3714560e/pkg/volume/gcepd/gce_pd.go#L382-L384

While it would be nice to do stricter validation, this does not need to block GA.