Add test for unknown elliptic curve supported by client

When TLS client sends a Supported Elliptic Curves Client Hello Extension
containing an unknown curve enum value, a server crashes with a
function_clause instead of just ignoring specified unknown curve.
Fix ssl server crash on unknown elliptic curve enum value

When TLS client sends Supported Elliptic Curves Client Hello Extension
server should select curves supported by both of them or refuse to
negotiate the use of an ECC cipher suite. So it should be OK to ignore
unknown curves specified by a client.