(fix) Disable libvirt service

- Rearrange Dockerfile layers to run the systemd link
  deletion statement to after the install of the libvirtd
  package

Change-Id: I49b0cb4ef4ebf6e92d2f99a7137387a5018ed3b5

images/maas-rack-controller/Dockerfile

@@ -3,7 +3,17 @@ FROM ubuntu:16.04
 ENV DEBIAN_FRONTEND noninteractive
 ENV container docker
 
+
+# everything else below is to setup maas into the systemd initialized
+# container based on ubuntu 16.04
+RUN apt-get -qq update && \
+    apt-get -y install \
+    sudo \
+    software-properties-common \
+    libvirt-bin \
+    systemd
 # Don't start any optional services except for the few we need.
+
 RUN find /etc/systemd/system \
          /lib/systemd/system \
          -path '*.wants/*' \
@@ -13,19 +23,6 @@ RUN find /etc/systemd/system \
          -exec rm \{} \;
 RUN systemctl set-default multi-user.target
 
-# everything else below is to setup maas into the systemd initialized
-# container based on ubuntu 16.04
-RUN apt-get -qq update && \
-    apt-get -y install \
-    sudo \
-    software-properties-common \
-    libvirt-bin
-
-# TODO(alanmeadows)
-# we need systemd 231 per https://github.com/systemd/systemd/commit/a1350640ba605cf5876b25abfee886488a33e50b
-#RUN add-apt-repository ppa:pitti/systemd -y && add-apt-repository ppa:maas/stable -y && apt-get update
-RUN apt-get install -y systemd
-
 # install syslog and enable it
 RUN apt-get install -y rsyslog
 RUN systemctl enable rsyslog.service
@@ -45,6 +42,7 @@ RUN systemctl enable register-rack-controller.service
 RUN mv /usr/sbin/tcpdump /usr/bin/tcpdump
 RUN ln -s /usr/bin/tcpdump /usr/sbin/tcpdump
 
+# echo journalctl logs to the container's stdout
 COPY scripts/journalctl-to-tty.service /etc/systemd/system/journalctl-to-tty.service
 RUN mkdir -p /etc/systemd/system/basic.target.wants ;\
     ln -s /etc/systemd/system/journalctl-to-tty.service /etc/systemd/system/basic.target.wants/journalctl-to-tty.service