api: reset the context before checking the config parameters in ngl_configure()
api: reset the context before checking the config parameters in ngl_configure()

This makes the behavior of ngl_configure() consistent in case of errors
(by always leaving the context un-configured).

gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl