fix locale warning during docker build

/usr/share/locale/locale.alias is a symlink to /etc/locale.alias and
needed by locale-gen.  /usr/share/locale/locale.alias gets normally
installed by locale package but is filtered in jessie-slim, so re-add
the symlink.

Signed-off-by: Mustafa Yücel <mustafa.yuecel@siemens.com>

Dockerfile

@@ -5,7 +5,8 @@ FROM debian:jessie-slim
 ENV LOCALE=en_US.UTF-8
 RUN apt-get update && \
     apt-get install --no-install-recommends -y locales && \
-    sed -i -e "s/# $LOCALE.*/$LOCALE UTF-8/" /etc/locale.gen && \
+    sed -i -e "s/# $LOCALE/$LOCALE/" /etc/locale.gen && \
+    ln -s /etc/locale.alias /usr/share/locale/locale.alias && \
     dpkg-reconfigure --frontend=noninteractive locales && \
     apt-get install --no-install-recommends -y \
                        gawk wget git-core diffstat unzip file \