unit-test: Use the built-in autoconf-archive

2016-09-16 is too old for the version of lcov that comes with
newer containers. To enable test coverage inside of our unit
test docker, we need a newer autoconf-archive. Use the built in
autoconf-archive as it should be maintained at a similar pace to
other tooling.

Tested:
    sdbusplus with coverage now builds successfully
    phosphor-logging still builds with no changes.

Change-Id: I751aa1c4312603466006b86772be7bfb0aa89dc5
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 63bacbc..26ff544 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -71,6 +71,7 @@
     python3-setuptools \
     pkg-config \
     autoconf \
+    autoconf-archive \
     libsystemd-dev \
     libssl-dev \
     libevdev-dev \
@@ -91,10 +92,6 @@
 RUN pip install inflection
 RUN pip install pycodestyle
 
-RUN wget http://ftpmirror.gnu.org/autoconf-archive/autoconf-archive-2016.09.16.tar.xz
-RUN tar -xJf autoconf-archive-2016.09.16.tar.xz
-RUN cd autoconf-archive-2016.09.16 && ./configure --prefix=/usr && make && make install
-
 # Googletest doesn't support pkg-config properly and therefore yocto uses a
 # patch to fix it.  This grabs and applies that patch and then builds it.
 RUN wget https://github.com/google/googletest/archive/release-1.8.0.tar.gz