🐛 Restricts AZ limit to 1 in e2e tests

[gab-satchi]

What this PR does / why we need it:
The e2e tests have been failing for a while: https://k8s-testgrid.appspot.com/sig-cluster-lifecycle-cluster-api-provider-aws#periodic-e2e-v1alpha3&width=20
They all seem to hit the 20 minute timeout while waiting for the cluster to reach InfrastructureReady. One of the recent changes that increased the time needed for an AWScluster to reach ready is the subnet defaulting logic #1721

These changes restrict the number of AZs to provision infrastructure to 1. While testing locally, this made an improvement from 12 minutes down to 5 minutes.
Note: We still have a test case that specifies subnets in multiple AZs and validates machines are created appropriately but there is now a gap in e2e testing the defaulting logic.

[gab-satchi]

It's not ideal to have most test cases not exercising the default behaviour so if it's better to just increase the timeout, I could update it.

[k8s-ci-robot]

@gab-satchi: The specified target(s) for /test were not found.
The following commands are available to trigger jobs:

• /test pull-cluster-api-provider-aws-test
• /test pull-cluster-api-provider-aws-build
• /test pull-cluster-api-provider-aws-integration
• /test pull-cluster-api-provider-aws-verify
• /test pull-cluster-api-provider-aws-make-conformance
• /test pull-cluster-api-provider-aws-e2e
• /test pull-cluster-api-provider-aws-e2e-conformance

Use /test all to run the following jobs:

• pull-cluster-api-provider-aws-test
• pull-cluster-api-provider-aws-build
• pull-cluster-api-provider-aws-integration
• pull-cluster-api-provider-aws-verify

In response to this:

/test periodic-cluster-api-provider-aws-e2e-v1alpha3

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[gab-satchi]

/test pull-cluster-api-provider-aws-e2e

[randomvariable]

I've been avoiding doing this in favour of fixing up the new e2e tests in #1760

[randomvariable]

/retest

[randomvariable]

/test pull-cluster-api-provider-aws-test

[randomvariable]

/test pull-cluster-api-provider-aws-test

[randomvariable]

I'm going to
/lgtm
this and open an issue to restore the defaults when we have time to sort it out.

[detiber]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: detiber

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [detiber]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment