Prevent noVNC loading error when invalid property is set on object

Util.set_defaults should accommodate with missing properties to prevent
'Uncaught TypeError: Cannot read property 'call' of undefined' error.
Fix invalid updateState property of RFB

It was changed to `onUpdateState` in
b1dee9478815b22bf5fee3ee9e44321d4bb46c91.
Merge pull request #391 from mandre/fix_invalid_property

Fix invalid updateState property on RFB preventing noVNC to load