[9] RFR: 8074531: Remove javax.security.cert.X509Certificate usage in internal networking packages

[Jason Uh]

Please review this change, which removes methods in internal net 
packages that use the deprecated javax.security.cert.X509Certificate type.

webrev: http://cr.openjdk.java.net/~juh/8074531/00/
bug: https://bugs.openjdk.java.net/browse/JDK-8074531
Thanks,
Jason