Cleanup Systemd files and add Travis-CI test for Systemd

.travis.yml

@@ -15,3 +15,6 @@ script:
 
   # Verify Ansible is available in the container.
   - docker exec --tty test-container env TERM=xterm ansible --version
+
+  # Verify that Systemd is working
+  - docker exec --tty test-container env TERM=xterm sh -c 'systemctl status --no-pager'

Dockerfile

@@ -16,6 +16,16 @@ RUN apt-get update \
     && apt-get clean
 RUN sed -i 's/^\($ModLoad imklog\)/#\1/' /etc/rsyslog.conf
 
+# Cleanup unwanted systemd files -- See https://hub.docker.com/_/centos/
+RUN find /lib/systemd/system/sysinit.target.wants/* ! -name systemd-tmpfiles-setup.service -delete; \
+rm -f /lib/systemd/system/multi-user.target.wants/*;\
+rm -f /etc/systemd/system/*.wants/*;\
+rm -f /lib/systemd/system/local-fs.target.wants/*; \
+rm -f /lib/systemd/system/sockets.target.wants/*udev*; \
+rm -f /lib/systemd/system/sockets.target.wants/*initctl*; \
+rm -f /lib/systemd/system/basic.target.wants/*;\
+rm -f /lib/systemd/system/anaconda.target.wants/*;
+
 # Install Ansible via Pip.
 RUN pip install $pip_packages