Update migrate-cf-mysql-to-pxc to use tls with credhub.
Update migrate-cf-mysql-to-pxc to use tls with credhub.

This matches the change in https://github.com/cloudfoundry/cf-deployment/commit/625d4b5cb7756ee3c89de74acdb39157cf19214a
[#160329126]

cloudfoundry/cf-deployment,cloudfoundry/cf-deployment