RFR[14] JDK-8234727: sun/security/ssl/X509TrustManagerImpl tests support TLSv1.3

[sha.jiang at oracle.com]

Hi,
Because the below tests use MD5withRSA certificates, so TLSv1.3 cannot 
be used.
test/jdk/sun/security/ssl/X509TrustManagerImpl/BasicConstraints.java
test/jdk/sun/security/ssl/X509TrustManagerImpl/SelfIssuedCert.java

This fix just re-generates the certificates to use SHA256withRSA.

Issue: https://bugs.openjdk.java.net/browse/JDK-8234727
Webrev: http://cr.openjdk.java.net/~jjiang/8234727/webrev.00/

Best regards,
John Jiang