cg: don't save cgroup directories twice

The path in cc->path here always has a "/" prefix since it comes from
/proc/$pid/cgroup. The additional / confuses the string slinging because ftw()
normalizes paths to have one "/" when we start traversing a subdirectory.
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cgroup.c

@@ -385,7 +385,7 @@ static int collect_cgroups(struct list_head *ctls)
 			strcpy(mount_point, prefix);
 		}
 
-		snprintf(path, PATH_MAX, "%s/%s", mount_point, cc->path);
+		snprintf(path, PATH_MAX, "%s%s", mount_point, cc->path);
 
 		current_controller = NULL;