Fix sr_self_test removal issue

[AndriyPt]

Removing sr_self_test by this PR #102 caused kinetic-devel version of one-liner to fail
sr_robot_lib: Cannot locate rosdep definition for [sr_self_test]
This is because sr_robot_lib is still dependent on sr_self_test.
Please fix it as it making one-liner for kinetic to fail and no Docker image can be built.

[toliver]

This should be fixed in this PR shadow-robot/sr-ros-interface-ethercat#160

Although it's not passing on jenkins as of now.