Fix NoSuchOptError wrt CONF.validation.ssh_key_type

This option isn't available in older versions of tempest,
since manila-tempest-plugin is branchless, we will need to
handle this situation gracefully.

Currently, all scenario tests with stable/train are failing.
Sample failure: https://paste.opendev.org/show/b9HiHJHTNbtL1z6Emnpe/

Change-Id: I36d5b5a32f27065c42e31ff231c55fc16bf18fda
Signed-off-by: Goutham Pacha Ravi <gouthampravi@gmail.com>
1 file changed