Ensure Go binaries use /etc/hosts first.

Go <1.16 has unexpected default behavior when the /etc/nsswitch.conf
file is missing: It will default to making a network request before
looking in local files like /etc/hosts. Unfortunately the very popular
alpine images do not have /etc/nsswitch.conf by default and so we must
create one ourselves.

There are many reports of this causing issues with name resolution:

golang/go#22846
golang/go#35305

Until this is fixed in a released version of Go (hopefully 1.16) we need
this change to ensure lookups happen in the expected way (files and then
network).

Change-Id: I246a767ae2767f0f83bf3b4229938a292cf9737e

cmd/authservice/Dockerfile

@@ -14,6 +14,7 @@ VOLUME /root/.local/share/storj/authservice
 HEALTHCHECK --interval=10s --timeout=3s --start-period=5s \
   CMD ["/app/authservice", "--log.level=error", "health-check"]
 
+RUN echo 'hosts: files dns' > /etc/nsswitch.conf
 COPY release/${TAG}/authservice_linux_${GOARCH:-amd64} /app/authservice
 COPY cmd/authservice/entrypoint /entrypoint
 

cmd/gateway-mt/Dockerfile

@@ -1,13 +1,21 @@
 ARG DOCKER_ARCH
 FROM ${DOCKER_ARCH:-amd64}/alpine
+
 ARG TAG
 ARG GOARCH
+
 ENV GOARCH ${GOARCH}
+
 EXPOSE 7777
 WORKDIR /app
+
 VOLUME /root/.local/share/storj/gateway-mt
+
+RUN echo 'hosts: files dns' > /etc/nsswitch.conf
 COPY release/${TAG}/gateway-mt_linux_${GOARCH:-amd64} /app/gateway-mt
 COPY cmd/gateway-mt/entrypoint /entrypoint
+
 ENTRYPOINT ["/entrypoint"]
+
 ENV STORJ_CONFIG_DIR=/root/.local/share/storj/gateway-mt
 ENV STORJ_SERVER_ADDRESS=0.0.0.0:7777