Cleanup Dockerfile

Dockerfile

@@ -3,11 +3,12 @@ FROM jlesage/baseimage-gui:ubuntu-16.04
 ENV APP_NAME="iDRAC 6" \
     IDRAC_PORT=443
 
-RUN apt-get update
-RUN apt-get -y install software-properties-common 
-RUN add-apt-repository ppa:openjdk-r/ppa  
-RUN apt-get update
-RUN apt-get -y install openjdk-7-jdk
+RUN apt-get update && \
+    apt-get install -y software-properties-common && \
+    add-apt-repository ppa:openjdk-r/ppa && \
+    apt-get update && \
+    apt-get install -y openjdk-7-jdk && \
+    && rm -rf /var/lib/apt/lists/*
 
 RUN mkdir /app && \
     chown ${USER_ID}:${GROUP_ID} /app