Add a comment with rationale for `MESOS_HOSTNAME_LOOKUP=false` in DC/OS.
Add a comment with rationale for `MESOS_HOSTNAME_LOOKUP=false` in DC/OS.

mesosphere-mergebot/mergebot-test-dcos,mesosphere-mergebot/dcos,GoelDeepak/dcos,GoelDeepak/dcos,dcos/dcos,kensipe/dcos,dcos/dcos,dcos/dcos,GoelDeepak/dcos,mesosphere-mergebot/dcos,mesosphere-mergebot/mergebot-test-dcos,mesosphere-mergebot/mergebot-test-dcos,GoelDeepak/dcos,dcos/dcos,dcos/dcos,kensipe/dcos,mesosphere-mergebot/mergebot-test-dcos,kensipe/dcos,kensipe/dcos,mesosphere-mergebot/dcos,mesosphere-mergebot/dcos