RFR: 8193892: Impact of noncloneable MessageDigest implementation

[Seán Coffey]

Looking to push a new test which helps test CloneableDigest code. It's 
something that arose during JDK-8193683 fix.

The test was contributed by Brad Wetmore. I've converted it to use the 
SSLSocketTemplate.

JBS : https://bugs.openjdk.java.net/browse/JDK-8193892
webrev : http://cr.openjdk.java.net/~coffeys/webrev.8193892/webrev/

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Regards,
Sean.