rosnode) rosnode_ping to raise exception when socket.err occurs. Also, enable test_rosnode.py that's not been run by rosnode.test.
Merge branch 'groovy-devel' into groovy-devel-rosnode-ping

Conflicts:
	tools/rosnode/src/rosnode/__init__.py
	tools/rosnode/test/rosnode.test
	tools/rosnode/test/test_rosnode.py