TW-53210 disable gssapi-with-mic ssh authentication

TW-53210 disable gssapi-with-mic ssh authentication

It wasn't supported in the trilead-based ssh client (used before
2017.2.1), so disabling it should not break anything. Problem with
gssapi-with-mic is that by default java asks a user for credentials and
waits for input from stdin, as a result checkout fails by timeout.

Also now we specify a custom security callback handler instead of the
default one which uses stdin. Our handler doesn't provide any
credentials, but will work if the agent machine already has the required
kerberos ticket.