Strip ros_packages/ from paths. ros_packages is only for avoiding to crawl the
whole /usr but the real one in the path without it.

Index: rospkg-1.1.0/src/rospkg/rospack.py
===================================================================
--- rospkg-1.1.0.orig/src/rospkg/rospack.py
+++ rospkg-1.1.0/src/rospkg/rospack.py
@@ -59,6 +59,7 @@ def list_by_path(manifest_name, path, ca
     path = os.path.abspath(path)
     basename = os.path.basename
     for d, dirs, files in os.walk(path, topdown=True, followlinks=True):
+        d = d.replace('ros_packages/', '')
         if 'CATKIN_IGNORE' in files:
             del dirs[:]
             continue  # leaf