Restore proxy settings in the windows registry when IE is quit

Restores proxy settings in the windows registry when IE is quit in addition to in the shutdown hook when handled by the driver. InternetExplorerDriver sets the proxy (unless handled by IEDriverServer) but cleans it up only when the JVM is quit. This causes any proxy settings to be active forever in a dedicated testing node on a grid. Any original proxy settings are lost forever if two different runs set different proxy servers, as the second run overwrites the backup of the original settings.

See http://code.google.com/p/selenium/issues/detail?id=5831 for more details.

The CLA is signed on behalf of my employer, Vaadin Ltd.