This patch adds a check "ParamsOauth2ClientCert.certificateRef"
when using OAuth 2.0 Mutual-TLS for authentication.
Also refactor the functions related to
SubscriptionAuthentication in common_script_utils.
Implements: blueprint support-oauth2-mtls
Implements: blueprint enhance-http-client
Change-Id: I9bcf4957ac8b173695e416fd56a0c3f3065e0c9f