Dockerfile-test: add test image with Go 1.9

Not to be blocked on Go 1.9 migration by CIs
(e.g. Semaphore CI not supporting Go 1.9).

Signed-off-by: Gyu-Ho Lee <gyuhox@gmail.com>

Dockerfile-test

@@ -0,0 +1,22 @@
+FROM golang:1.9-stretch
+
+RUN apt-get -y update
+RUN apt-get -y install \
+  netcat \
+  libaspell-dev \
+  libhunspell-dev \
+  hunspell-en-us \
+  aspell-en \
+  shellcheck
+
+RUN mkdir -p ${GOPATH}/src/github.com/coreos/etcd
+WORKDIR ${GOPATH}/src/github.com/coreos/etcd
+
+ADD ./scripts/install-marker.sh ./scripts/install-marker.sh
+
+RUN go get -v -u -tags spell github.com/chzchzchz/goword \
+  && go get -v -u github.com/coreos/license-bill-of-materials \
+  && go get -v -u honnef.co/go/tools/cmd/gosimple \
+  && go get -v -u honnef.co/go/tools/cmd/unused \
+  && go get -v -u honnef.co/go/tools/cmd/staticcheck \
+  && ./scripts/install-marker.sh amd64