Implementing ListSnapshots

[zacharya]

Is this a bug fix or adding new feature?
Fixes: #233

What is this PR about? / Why do we need it?
This implements ListSnapshots from the CSI spec (not yet used by Kubernetes).

What testing is done?
Unit tests have been written for driver and cloud packages that handle both happy path and error cases.

[k8s-ci-robot]

Hi @zacharya. Thanks for your PR.

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[coveralls]

Pull Request Test Coverage Report for Build 623

• 104 of 114 (91.23%) changed or added relevant lines in 2 files are covered.
• 115 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+1.7%) to 70.966%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/cloud/cloud.go	49	51	96.08%
pkg/driver/controller.go	55	63	87.3%

Files with Coverage Reduction	New Missed Lines	%
pkg/cloud/cloud.go	56	75.26%
pkg/driver/controller.go	59	72.05%

Totals
Change from base Build 607:	1.7%
Covered Lines:	1073
Relevant Lines:	1512

---

💛 - Coveralls

[leakingtapan]

/ok-to-test

[leakingtapan]

Overall LGTM. Left some comments. Also could you add some details on how is this being tested?

[leakingtapan]

Since controller.ListSnapshots already has logic to guarantee maxResults >= 5, as cloud is an internal struct, I feel we can just set describeSnapshotsInput.MaxResults = aws.Int64(maxResults) without checking if maxResults >= 5 {.

[zacharya]

I just pushed another commit that enabled ListSnapshot sanity testing. In order to satisfy the unit tests from the sanity testing packages, I had to push the logic down into the cloud package so controller was able to handle 0 < MaxEntries < 5. Let me know how you want to proceed with this. It's mostly cosmetic as we're just using fakeCloudProvider anyways.

[leakingtapan]

If that's what the sanity test checks, im okay with the change.

[zacharya]

/retest

[leakingtapan]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: leakingtapan, zacharya

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[leakingtapan]

/retest

[zacharya]

/retest