12.6.5223 - Packaging update

• [DEBIAN] use the new GPG signing key for the apt.datadoghq.com repository
• [DEBIAN] fix the status command
• [ALL IMAGES] add support for max_traces_per_second option to datadog.conf #291
• [DEBIAN] update the Debian base image to stretch
• [JMX] ship openjdk 8u151