fix(Dockerfiles): silence apt-get TTY warnings

The mesos components didn't all set DEBIAN_FRONTEND to
noninteractive, so there were several build warnings about
not finding a TTY. Additionally, some Alpine images still
had a vestigial DEBIAN_FRONTEND statement.

Author: mboersma

Dockerfile

@@ -1,7 +1,5 @@
 FROM alpine:3.1
 
-ENV DEBIAN_FRONTEND noninteractive
-
 # install common packages
 RUN apk add --update-cache curl bash sudo && rm -rf /var/cache/apk/*