Warn when Impala shell fails to connect due to tlsv1.2

When impala-shell is used to connect to an impala cluster with --ssl_minimum_version=tlsv1.2, if the Python version being used is < 2.7.9 the connection will fail due to a limitation of TSSLSocket. See IMPALA-6990 for more details

Currently, when this occurs, the error that gets printed is "EOF occurred in violation of protocol", which is not very helpful. We should detect this situation and print a more informative warning