Honour ssh_key_type config for keypair and ssh clients

With [1] Tempest added support for 'ecdsa' key types
using a new config option validation.ssh_key_type.

Let's honour this while creating ssh and keypair
clients. This is needed atleast for latest openssl
package in CentOS 9-stream where support for 'rsa'
key is dropped.

[1] https://review.opendev.org/c/openstack/tempest/+/807465

Closes-Bug: #1963907
Change-Id: I1e4621ca9c02231d02df09fa758eae5c55eb0f93
5 files changed