Make debian frontend noninteractive to prevent install from getting stuck

Author: milindl

.semaphore/semaphore.yml

@@ -126,6 +126,7 @@ blocks:
           value: "0.02"
       prologue:
         commands:
+          - export DEBIAN_FRONTEND=noninteractive
           - wget -qO - https://packages.confluent.io/deb/7.7/archive.key | sudo apt-key add -
           - sudo add-apt-repository -y "deb https://packages.confluent.io/clients/deb $(lsb_release -cs) main"
           - sudo apt-get update