Adds two new VirtualMedia fields: Certificates and VerifyCertificate.
The former currently points at an empty collection, which cannot be
updated. The latter can be set via PATCH on a VirtualMedia resource.
TLS certificate validation has been disabled by default to match what
actual hardware does.
Change-Id: If0090b865d2106b90a13f9ca7329db6f8de6fc8a