add tls support and tests to connect-init command

[kschoche]

Changes proposed in this PR:

• Add TLS tests to connect-init/command_test.go
• Modify the common.GenerateServerCerts function to do it's own cleanup and propogate this to existing tests.
  The reason for this is that it helped to clean up my test so that I didn't have to generate server certs when TLS is disabled in the table test due to scoping of the cleanup func, as well as it generally cleans up existing code.
• Remove old copy of generateServerCerts from server-acl-init test and convert it to the one in common.
• In case it isn't obvious connect-init already works with TLS so no actual code is changed. Inside of connect-inject/container_init.go we are passing in the required ENV variables in the command template to enable it to be picked up by the consul client:

const initContainerCommandTpl = `
{{- if .ConsulCACert}}
export CONSUL_HTTP_ADDR="https://${HOST_IP}:8501"
export CONSUL_GRPC_ADDR="https://${HOST_IP}:8502"
export CONSUL_CACERT=/consul/connect-inject/consul-ca.pem
cat <<EOF >/consul/connect-inject/consul-ca.pem
{{ .ConsulCACert }}
EOF
{{- else}}
export CONSUL_HTTP_ADDR="${HOST_IP}:8500"
export CONSUL_GRPC_ADDR="${HOST_IP}:8502"
{{- end}}
consul-k8s connect-init -pod-name=${POD_NAME} -pod-namespace=${POD_NAMESPACE} \
  {{- if .AuthMethod }}

How I've tested this PR:
Unit tests have been updated to enable TLS and pass.
Manually tested TLS enabled with a deployment.

How I expect reviewers to test this PR:
Unit tests have been updated to enable TLS and pass.
Manually tested TLS enabled with a deployment.

Checklist:

• Tests added
• CHANGELOG entry added (HashiCorp engineers only, community PRs should not add a changelog entry)

[lkysow]

Nice work! Good catch on the generate certs duplication.

[ishustava]

Looks great 🎉 !! Thanks for adding these tests 🙏

[ishustava]

Great! I really like this pattern!

[ishustava]

nice catch!