Code Review Request of JDK-8157035 Use stronger algorithms and keys for JSSE testing

[Xuelei Fan]

Hi,

Please review this test update:
   http://cr.openjdk.java.net/~xuelei/8157035/webrev.00/

test/javax/net/ssl/etc/keystore and truststore are used a lot for X.509
cert based SSL/TLS authentication in JDK testing.  MD5 and SHA1 are used
as the signature algorithms. The key size of EC certs is 192 bits.

MD5 has been disabled, and 192-bits EC keys will be disabled in the near
future(see JDK-8148516).  It's time to use stronger algorithms (SHA256)
and keys (2048-bits for RSA and 256-bits for EC).

This update renew the RSA cert with 2048-bits key and the EC cert with
256-bits key.  And the hash algorithms of the signatures are now SHA256.

Note that the DSA entry is not updated this time.

Thanks,
Xuelei