Add 'cf-' to datadog diego tags
Add 'cf-' to datadog diego tags

This is to be more consistent with the other deploy tags.

Signed-off-by: Kris Hicks <0e803ac6659de70b605624a656fb953ee9b9fc40@gmail.com>

cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release,cloudfoundry-incubator/diego-release