Add default openssl.cnf and script fixes

[notexactlyawe]

Description

This pull request fixes a syntax error in clean_oai_on_k8s and changes generate_certs to use a default openssl.cnf if it doesn't exist.

The file openssl.cnf.default is filled to the best of my knowledge with sensible defaults (but I am new to OpenSSL so feedback would be welcome). The HSS and MME boot happily under certificates generated by this script on my k8s cluster.

Motivation and Context

For my undergraduate dissertation, I'm looking at scaling the EPC on Kubernetes and so this repository has been super helpful. When I tried to deploy this repo, however, the HSS crashed because of bad certificates and this script wasn't working because my environment doesn't have a default openssl.cnf.

After creating a default configuration and running this script with it, my deployment all worked so I'm upstreaming this change in case it's helpful to anyone else.

For reference, my cluster is running on POWDER and configuration can be found in notexactlyawe/honours-project. It is based off kubeadm and flannel.

How Has This Been Tested?

• Covered by existing integration testing
• Added integration testing to cover
• Tested locally
• Have not tested

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.