Make apt-get install list in dockerfiles for trusty-common and precise-common more readable

docker/build/precise-common/Dockerfile

@@ -13,7 +13,14 @@ RUN apt-get -y install sudo
 RUN useradd docker && echo "docker:docker" | chpasswd
 RUN echo "docker ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers
 RUN mkdir -p /home/docker && chown -R docker:docker /home/docker
-RUN apt-get install -y python2.7 python2.7-dev python-pip python-apt python-yaml python-jinja2 git
+RUN apt-get install -y \
+    python2.7 \
+    python2.7-dev \
+    python-pip \
+    python-apt \
+    python-yaml \
+    python-jinja2 \
+    git
 
 # Temporary hacking related to an SELinux bug.  This issue causes, at least,
 # useradd to fail silently when the -m flag is passed in.  The bug affects

docker/build/trusty-common/Dockerfile

@@ -13,7 +13,15 @@ RUN apt-get -y install sudo
 RUN useradd docker && echo "docker:docker" | chpasswd
 RUN echo "docker ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers
 RUN mkdir -p /home/docker && chown -R docker:docker /home/docker
-RUN apt-get install -y python2.7 python2.7-dev python-pip python-apt python-yaml python-jinja2 git
+RUN apt-get install -y \
+    python2.7 \
+    python2.7-dev \
+    python-pip \
+    python-apt \
+    python-yaml \
+    python-jinja2 \
+    git
+
 USER docker
 
 # ansible bootstrap