GUAC-1115: Ensure LDAP connection is always cleaned up.

extensions/guacamole-auth-ldap/src/main/java/org/glyptodon/guacamole/auth/ldap/AuthenticationProviderService.java

@@ -209,6 +209,7 @@ public class AuthenticationProviderService {
             catch (UnsupportedEncodingException e) {
                 logger.error("Unexpected lack of support for UTF-8: {}", e.getMessage());
                 logger.debug("Support for UTF-8 (as required by Java spec) not found.", e);
+                disconnect(ldapConnection);
                 return null;
             }