Added env arg demo

Mar21/ENVARGDemo/EnvDemo/Dockerfile

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+FROM openjdk:8
+# base image is openjdk
+LABEL author="khaja ibrahim"
+LABEL maintainer="qtdevops@gmail.com"
+ENV applicationpath='/springpetclinic.jar'
+ENV dummy='dummy'
+ARG downloadlocation
+# Downloading the image from the url
+ADD  ${downloadlocation} ${applicationpath}
+# spring pet clinic runs on port 8080
+EXPOSE 8080
+# command to start the application
+CMD ["java",  "-jar",  ${applicationpath} ]