Merge pull request #271 from esteve/fix-systemd-service

roslaunch: removed ros-set-cmake-prefix dependency

recipes-ros/ros-comm/roslaunch/roscore.service

 [Unit]
 Description=Launcher for the ROS master, parameter server and rosout logging node
-After=network.target ros-set-cmake-prefix
+After=network.target
 
 [Service]
 EnvironmentFile=/etc/default/roscore