allow setting default fs type through command line argument

[RomanBednar]

The external attacher was using a hardcoded default ext4 filesystem which was applied when PV spec did not contain fstype.

As a result attacher always reported ext4 as fs_type volume capability creating interference with some CSI drivers.

This patch adds a flag to csi-attacher binary which provides users with a workaround to set their own default filesystem or simply disable the interference by using an empty string:

./bin/csi-attacher --default-fstype ""

When the flag is not used we still use ext4, next major release will allow behavior change and we can default to "" instead preserving the argument in case it's ever needed.

/kind bug

Which issue(s) this PR fixes:
Fixes #287

Does this PR introduce a user-facing change?:

There is a new --default-fstype flag available in this release that defaults to ext4 and can be used to set any value a driver may need. In the next major release ext4 as the default fsType will be deprecated and replaced by ""

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[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Roman Bednář (dd0d1c4)

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[k8s-ci-robot]

Hi @RomanBednar. Thanks for your PR.

I'm waiting for a kubernetes-csi member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[jsafrane]

/ok-to-test

[jsafrane]

Please update also README.md and add a release note to the inital comment of this PR - this is an user facing change.
It should clearly say that ext4 as the default fsType is deprecated and will be replaced by "" in the next major release. And there is --default-fstype available in this release that can be used to set it explicitly to any value a driver may need.

[jsafrane]

/check-cla

[RomanBednar]

i signed it

[RomanBednar]

I signed it

[jsafrane]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jsafrane, RomanBednar

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