Fixed a comparison and logical statement order issue.

[Nurgak]

The scene parameter is None by default, this is not equal to 0 or False, therefore it passed the comparison anyway and gave the following error:

File "/home/karl/catkin_ws/src/moveit_python/src/moveit_python/pick_place_interface.py", line 268, in pick_with_retry
if name in scene.getKnownAttachedObjects():
AttributeError: 'NoneType' object has no attribute 'getKnownAttachedObjects'

Second problem in there was the logical statement order, as or precedes and. So even when fixing the scene parameter comparison with None it passed this block and threw the same error. I added parenthesis as a quick solution.