Fix headnode_{create,delete}_hnic

First, fix the API.
Second, fix the typo in the CLI.

This should now work.

Closes #138
Add parameter 'nodename' to 'headnode_delete_hnic'
Add two more tests to headnode_delete_hnic
Merge branch 'devel' into bug138

Conflicts:
	haas/cli.py
Merge pull request #144 from gsilvis/bug138

Fix headnode_{create,delete}_hnic