test: check AKS agentpool provisioning state before upgrading

[chewong]

Reason for Change:

Fixes #417.

Requirements

• squashed commits
• included documentation
• added unit tests and e2e tests (if applicable).

Issue Fixed:

Please answer the following questions with yes/no:

Does this change contain code from or inspired by another project? If so, did you notify the maintainers and provide attribution?

• yes
• no

Notes for Reviewers:

[chewong]

Waiting for the agent pool to be in succeeded provisioning state (attempt 0)
Waiting for the agent pool to be in succeeded provisioning state (attempt 1)
Agent pool is in succeeded provisioning state