Add non-negative check on getVolumeLimit()

[gtxu]

Is this a bug fix or adding new feature?
Fix #1361
What is this PR about? / Why do we need it?
When volume attach limit not correct calculated, it may return negative value which is not allowed in the csi/spec
The -1 return in the issue reflect to metadata_ec2.go, when all available volume attached, the ENI turns to be actually ENI +1 for Nitro instances.

Reproduce the issue
On a cluster with aws-ebs-csi-driver installed,

1. create a nitro instance node
2. schedule pods with pvc to the node till reach/or exceed the attach limit
3. restart aws-ebs-csi-driver
4. check kubectl log, find the same error message as the issue Invalid attach limit value -1 cannot be added to CSINode object for "ebs.csi.aws.com" #1361

What testing is done?
Unit test added for maximum volume/eni allocated cases
CI test passed

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[gtxu]

/test all

[torredil]

• Suggest providing a minimal reproducible example of Invalid attach limit value -1 cannot be added to CSINode object for "ebs.csi.aws.com" #1361.
• Suggest adding details to What testing is done? section.

[gtxu]

• Suggest providing a minimal reproducible example of Invalid attach limit value -1 cannot be added to CSINode object for "ebs.csi.aws.com" #1361.

• Suggest adding details to What testing is done? section.

Adding reproducible example and test cases for the change. Thanks for the feedback folks!

[ConnorJC3]

/lgtm

👍

[torredil]

/lgtm

[ConnorJC3]

/hold need to test this on Windows, might expose an existing bug

[ConnorJC3]

/remove-hold
All good

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hanyuel, torredil

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