[geneus] Check eus2 permission 

check eus2 permission to avoid following error:
```
  /home/travis/ros/ws_jsk_demos/src/jsk-ros-pkg/jsk_roseus/geneus/scripts/genmsg_eus: line 7: /home/travis/ros/ws_jsk_demos/src/jsk-ros-pkg/jsk_roseus/euslisp/jskeus/eus/Linux64/bin/eus2: Permission denied
```