Fix Dockerfiles

* Install apt-transport-https depency in Debian based containers
* Test different CMD instruction in CentOS 6 container

tests/dockerfiles/Dockerfile.centos-6

@@ -9,4 +9,4 @@ RUN echo -e '[local]\nlocalhost ansible_connection=local' > /etc/ansible/hosts
 
 VOLUME ["/sys/fs/cgroup"]
 
-CMD ["/usr/sbin/init"]
+CMD ["/sbin/init"]

tests/dockerfiles/Dockerfile.debian-jessie

@@ -8,6 +8,7 @@ RUN apt-get update -y && apt-get install -y --no-install-recommends \
     python-dev \
     python-pip \
     git \
+    apt-transport-https
  && rm -rf /var/lib/apt/lists/*
 
 RUN pip install --upgrade setuptools && pip install ansible

tests/dockerfiles/Dockerfile.debian-stretch

@@ -9,6 +9,7 @@ RUN apt-get update -y && apt-get install -y --no-install-recommends \
     python-pip \
     git \
     systemd \
+    apt-transport-https
  && rm -rf /var/lib/apt/lists/*
 
 RUN pip install --upgrade setuptools && pip install ansible

tests/dockerfiles/Dockerfile.ubuntu-trusty

@@ -5,6 +5,7 @@ RUN apt-get update && apt-get dist-upgrade -y && apt-get install -y software-pro
 RUN apt-add-repository -y ppa:ansible/ansible && apt-get update && apt-get install -y \
     git \
     ansible \
+    apt-transport-https
  && rm -rf /var/lib/apt/lists/*
 
 RUN echo "[local]\nlocalhost ansible_connection=local" > /etc/ansible/hosts

tests/dockerfiles/Dockerfile.ubuntu-xenial

@@ -5,6 +5,7 @@ RUN apt-get update && apt-get dist-upgrade -y && apt-get install -y software-pro
 RUN apt-add-repository -y ppa:ansible/ansible && apt-get update && apt-get install -y \
     git \
     ansible \
+    apt-transport-https
  && rm -rf /var/lib/apt/lists/*
 
 RUN echo "[local]\nlocalhost ansible_connection=local" > /etc/ansible/hosts