Unknown link warning should be printed once per link (ros ticket #4114)

[ahendrix]

The unknown link warning from the planning environment server should be printed once per link. It's really annoying.

{{{
Node: /environment_server_right_arm
Time: 1270344064.189029092
Severity: Warn
Location: /u/watts/ros/pkgs/collision_environment/collision_space/src/environmentODE.cpp:EnvironmentModelODE::updateAllowedTouch:1115
Published Topics: /rosout, /environment_server_contact_markers, /environment_server_right_arm/allowed_contact_regions_array

Unknown link r_gripper_led_frame specified for touch link
}}}

trac data:

• Owner: gjones
• Reporter: watts
• Reported at: Sat Apr 3 18:26:48 2010
• URL: https://code.ros.org/trac/wg-ros-pkg/ticket/4114