[jsk_perception] Fix nodehandle in point_pose_extractor

[nakane11]

This PR fixes the problem reported in #2778 and depends on #2778.
pnh was mistakenly used instead of nh by #2722.

Now the result of rosnode info /kinect_head/rgb/point_pose_extractor is here:

Node [/kinect_head/rgb/point_pose_extractor]
Publications: 
 * /diagnostics [diagnostic_msgs/DiagnosticArray]
 * /kinect_head/rgb/ObjectDetection [posedetection_msgs/ObjectDetection]
 * /kinect_head/rgb/ObjectDetection_agg [posedetection_msgs/ObjectDetection]
 * /kinect_head/rgb/object_pose [geometry_msgs/PoseStamped]
 * /kinect_head/rgb/point_pose_extractor/debug_image [sensor_msgs/Image]
 * /kinect_head/rgb/point_pose_extractor/debug_image/compressed [sensor_msgs/CompressedImage]
 * /kinect_head/rgb/point_pose_extractor/debug_image/compressed/parameter_descriptions [dynamic_reconfigure/ConfigDescription]
 * /kinect_head/rgb/point_pose_extractor/debug_image/compressed/parameter_updates [dynamic_reconfigure/Config]
 * /kinect_head/rgb/point_pose_extractor/debug_image/compressedDepth [sensor_msgs/CompressedImage]
 * /kinect_head/rgb/point_pose_extractor/debug_image/compressedDepth/parameter_descriptions [dynamic_reconfigure/ConfigDescription]
 * /kinect_head/rgb/point_pose_extractor/debug_image/compressedDepth/parameter_updates [dynamic_reconfigure/Config]
 * /kinect_head/rgb/point_pose_extractor/debug_image/theora [theora_image_transport/Packet]
 * /kinect_head/rgb/point_pose_extractor/debug_image/theora/parameter_descriptions [dynamic_reconfigure/ConfigDescription]
 * /kinect_head/rgb/point_pose_extractor/debug_image/theora/parameter_updates [dynamic_reconfigure/Config]
 * /rosout [rosgraph_msgs/Log]
 * /tf [tf2_msgs/TFMessage]

Subscriptions: 
 * /ImageFeature0D [unknown type]

Services: 
 * /kinect_head/rgb/SetTemplate
 * /kinect_head/rgb/point_pose_extractor/debug_image/compressed/set_parameters
 * /kinect_head/rgb/point_pose_extractor/debug_image/compressedDepth/set_parameters
 * /kinect_head/rgb/point_pose_extractor/debug_image/theora/set_parameters
 * /kinect_head/rgb/point_pose_extractor/get_loggers
 * /kinect_head/rgb/point_pose_extractor/list
 * /kinect_head/rgb/point_pose_extractor/load_nodelet
 * /kinect_head/rgb/point_pose_extractor/set_logger_level
 * /kinect_head/rgb/point_pose_extractor/unload_nodelet

[tkmtnt7000]

Thank you very much for quick fixing!
Could you add a test code that uses group namespace such as #2778 ?

[nakane11]

@tkmtnt7000 Thank you for your advice!
rostest succeeded.

[jsk_perception.rosunit-test_group_ns_point_pose_extractor/test_published][passed]

SUMMARY
 * RESULT: SUCCESS
 * TESTS: 1
 * ERRORS: 0
 * FAILURES: 0

[tkmtnt7000]

Thank you. I have confirmed that this pr worked on local pc and pr2, and test passed.