Issue project-sunbird/sunbird-commons#348 feat: ping down version of docker images

images/api-manager-jenkins-swarm-agent/Dockerfile

-FROM vfarcic/jenkins-swarm-agent
+FROM vfarcic/jenkins-swarm-agent:17.10.07-4
 
 USER root
 RUN apk --update add sudo && \

images/documentation-jenkins-swarm-agent/Dockerfile

-FROM vfarcic/jenkins-swarm-agent
+FROM vfarcic/jenkins-swarm-agent:17.10.07-4
 
 USER root
 RUN apk -v --update add ruby=2.4.1-r3 nodejs=6.10.3-r1 ruby-bundler=1.15.0-r0

images/proxy/Dockerfile

-FROM nginx:alpine
+FROM nginx:1.13.7-alpine
 
 RUN rm -rf /etc/nginx/conf.d
 

images/reporter-jenkins-swarm-agent/Dockerfile

-FROM vfarcic/jenkins-swarm-agent
+FROM vfarcic/jenkins-swarm-agent:17.10.07-4
 ENV CQLSH_VERSION=5.0.3
 
 RUN apk --update add tar curl && \
     pip install cassandra-driver
-    
+
 RUN mkdir -p /usr/var/cqlsh && \
     curl -SL https://pypi.python.org/packages/12/a7/13aff4ad358ff4abef6823d872154d0955ff6796739fcaaa2c80a6940aa6/cqlsh-${CQLSH_VERSION}.tar.gz \
     | tar xzvC /usr/var && \