Internal TLS: Use specific CA file for mysql-client

Internal TLS: Use specific CA file for mysql-client

Instead of using the CA bundle, this sets the mysql client configuration
file to use a specific file for validating the certificate of the
database server. This helps in two ways:

* Improves performance since validation will check only one certificate.
* Improves security since we're only the certificates signed by one CA
  are valid, instead of any certificate that the system trusts (which
  could include potentially compromised public certs).

Change-Id: I46f7cb6da73715f8f331337e0161418450d5afd7
Depends-On: I75bdaf71d88d169e64687a180cb13c1f63418a0f