RFR [15] JDK-8215711, Missing key_share extension for (EC)DHE key exchange should alert missing_extension

[Xuelei Fan]

Hi,

Could I have the following update reviewed?

     http://cr.openjdk.java.net/~xuelei/8215711/webrev.00/

In the current TLS implementation, if one of "supported_groups" 
extension and "key_share" extension is not present in the ClientHello 
handshake message, the internal_error alter will be used.  Per the spec 
(RFC 8846), the alert should be "missing_extension" alert.

The fuzzing test passed with this update.  No new regression test 
(noreg-external).

Thanks,
Xuelei