Rename unused mkws property "service_proxy_auth" to "authenticated".

Rename unused mkws property "service_proxy_auth" to "authenticated".
	(Better describes what it does, and avoids confusion with the
	mkws_config property of the same name.)
Check before running a search whether we're authenticated.
	(It's because we were not that auto-searches were failing on
	the first call of a new session -- the search was being sent
	before the authentication response was received.)