Change the ros2 package url

As the ros2 ci build farm has switched the ubuntu from Xenial to
Bionic(ros2/ci#148), we have to change the url
of the package url in order to get the right one.

Fix NONE

Dockerfile

@@ -33,7 +33,7 @@ RUN git config --global user.name $GIT_USER_NAME \
 ENV ROS2_WS=/root
 WORKDIR $ROS2_WS
 
-RUN wget http://ci.ros2.org/view/packaging/job/packaging_linux/lastSuccessfulBuild/artifact/ws/ros2-package-linux-x86_64.tar.bz2 \
+RUN wget https://ci.ros2.org/view/packaging/job/packaging_xenial_linux/lastSuccessfulBuild/artifact/ws/ros2-package-linux-x86_64.tar.bz2 \
     && tar xf ros2-package-linux-x86_64.tar.bz2
 
 RUN echo "source $ROS2_WS/ros2-linux/local_setup.bash" >> $HOME/.bashrc