Incorrect node name in default namespace

[gelin]

If the node is created like this:

node, err := ros.NewNode("nodename", os.Args)

The resulting node name registered on ROS master become "//nodename".

This causes the address of the node cannot be determined correctly and tools like multimaster_fkie cannot sync a master with such node.

$ rosnode list -a
unknown address         //nodename

[gelin]

Possible fix is here: gelin@62d827d