This commit fixes #47.

Also delete the urdf subdirectory from the installation list of the package husky_gazebo
since the directory doesn't exist.

HOW BUILT
$ catkin_make_isolated --install --use-ninja

HOW VERIFIED
$ roslaunch husky_gazebo husky_playpen.launch
$ roslaunch husky_viz view_robot.launch

Verify that the LiDAR is present on the gazebo husky and works as expected.

Change-Id: I8797d561489250417dc8fe2b49d958993ca7949c
Signed-off-by: Wei Ren <renwei@smartconn.cc>