RFR 8245520: Provide a way to add CA certificate to cacerts during test run

[sha.jiang at oracle.com]

Hi,
This patch contains a patched version for class 
sun.security.util.AnchorCertificates.
It allows to add CAs to cacerts at runtime for testing purpose.

Webrev: http://cr.openjdk.java.net/~jjiang/8245520/webrev.00/
Issue: https://bugs.openjdk.java.net/browse/JDK-8245520

Best regards,
John Jiang