tests/Dockerfile: revert back to ubuntu

Fedora is too big (550 MB),
while Ubuntu image is only 350 MB.

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

tests/Dockerfile

@@ -1,16 +1,33 @@
-FROM fedora:28
+FROM ubuntu:18.04
 
-RUN dnf check-update || true \
-  && dnf install --assumeyes \
-  git curl wget mercurial meld gcc gcc-c++ which \
-  gcc automake autoconf dh-autoreconf libtool libtool-ltdl \
-  tar unzip gzip \
-  aspell-devel aspell-en hunspell hunspell-devel hunspell-en hunspell-en-US ShellCheck nc || true \
-  && dnf check-update || true \
-  && dnf upgrade --assumeyes || true \
-  && dnf autoremove --assumeyes || true \
-  && dnf clean all || true \
-  && dnf reinstall which || true
+RUN rm /bin/sh && ln -s /bin/bash /bin/sh
+RUN echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
+
+RUN apt-get -y update \
+  && apt-get -y install \
+  build-essential \
+  gcc \
+  apt-utils \
+  pkg-config \
+  software-properties-common \
+  apt-transport-https \
+  libssl-dev \
+  sudo \
+  bash \
+  curl \
+  wget \
+  tar \
+  git \
+  netcat \
+  libaspell-dev \
+  libhunspell-dev \
+  hunspell-en-us \
+  aspell-en \
+  shellcheck \
+  && apt-get -y update \
+  && apt-get -y upgrade \
+  && apt-get -y autoremove \
+  && apt-get -y autoclean
 
 ENV GOROOT /usr/local/go
 ENV GOPATH /go
@@ -27,10 +44,6 @@ WORKDIR ${GOPATH}/src/github.com/coreos/etcd
 
 ADD ./scripts/install-marker.sh /tmp/install-marker.sh
 
-# manually link "goword" dependency
-# ldconfig -v | grep hunspell
-RUN ln -s /lib64/libhunspell-1.6.so /lib64/libhunspell.so
-
 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 github.com/mdempsky/unconvert \
@@ -44,4 +57,4 @@ RUN go get -v -u -tags spell github.com/chzchzchz/goword \
   && /tmp/install-marker.sh amd64 \
   && rm -f /tmp/install-marker.sh \
   && curl -s https://codecov.io/bash >/codecov \
-  && chmod 700 /codecov
+  && chmod 700 /codecov