[15] RFR: 8243138: Enhance BaseLdapServer to support starttls extended request

[Chris Yin]

Hello

Please review following change for enhancement to com/sun/jndi/ldap/lib/BaseLdapServer.java, thanks

Bug: https://bugs.openjdk.java.net/browse/JDK-8243138
Webrev: http://cr.openjdk.java.net/~xyin/8243138/webrev.00/

There is requirement to test starttls extended op against dummy ldap server, but unfortunately, current BaseLdapSever logic cannot handle it correctly since the starttls request is quite special to use existed socket for tls negotiate. This enhancement will provide the possibility to wrap current socket connection and overwrite in-place processing input/output stream, certainly, that will not affect existed tests which depends on BaseLdapServer. Run existed dependency tests on 4 platforms for total 200 times, all green.

Thanks,
Chris