Added Dockerfile to build sidecar as well as sample driver

Author: brahmaroutu

Dockerfile renamed to cmd/objectstorage-sidecar/Dockerfile

@@ -0,0 +1,6 @@
+FROM gcr.io/distroless/static:latest
+LABEL maintainers="Kubernetes Authors"
+LABEL description="Object Storage Sample Driver"
+
+COPY ./bin/sample-driver sample-driver
+ENTRYPOINT ["/sample-driver"]