Remove erroneous server_random filling

Commit e481f9b9 removed OPENSSL_NO_TLSEXT from the code.

Previously if OPENSSL_NO_TLSEXT *was not* defined then the server random was
filled during getting of the ClientHello. If it *was* defined then the
server random would be filled in ssl3_send_server_hello(). Unfortunately in
commit e481f9b9

 the OPENSSL_NO_TLSEXT guards were removed but *both*
server random fillings were left in. This could cause problems for session
ticket callbacks.

Reviewed-by: Stephen Henson <steve@openssl.org>