connector-server-jetty: migrate off deprecated org.eclipse.jetty.util.log.Log

[vharseko]

Follow-up to #115.

OpenICFWebSocketCreator and OpenICFWebSocketServletBase still use the deprecated org.eclipse.jetty.util.log.Log / Logger API (deprecated in Jetty 10/11, removed in Jetty 12). The endpoint class added in #115 (OpenICFWebSocket) already uses the framework's own org.identityconnectors.common.logging.Log.

Migrate the two remaining classes to org.identityconnectors.common.logging.Log for consistency and to unblock a future Jetty 12 upgrade.