Dockerfile: include ssl certificates (#371)

To allow for exporters or any outside service that needs TLS/SSL,
we need to include certificaticates e.g. for the Stackdriver exporter.

Author: basvanbeek

cmd/ocagent/Dockerfile

@@ -1,9 +1,13 @@
 # Use a helper to create an emtpy configuration since the agent requires such file
 FROM alpine:3.7 as helper
-RUN touch ./config.yaml
+RUN apk update \
+    && apk add --no-cache ca-certificates \
+    && update-ca-certificates \
+    && touch ./config.yaml
 
 FROM scratch
 COPY ocagent_linux /
 COPY --from=helper ./config.yaml config.yaml
+COPY --from=helper /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 ENTRYPOINT ["/ocagent_linux"]
 EXPOSE 55678 55679