Multiple fixes to test_server_basic_ops

* self.keypair has a private_key attribute, not private. This patch
fixes that.

* remote client connection is obtained but not validated. This patch
  adds that by calling validate_authentication()

Change-Id: I42f6bd65c746f86d7f5cc143e193dbb03503829b
diff --git a/tempest/scenario/test_server_basic_ops.py b/tempest/scenario/test_server_basic_ops.py
index d369f12..83bb144 100644
--- a/tempest/scenario/test_server_basic_ops.py
+++ b/tempest/scenario/test_server_basic_ops.py
@@ -149,10 +149,11 @@
             instance.add_floating_ip(floating_ip)
             # Check ssh
             try:
-                self.get_remote_client(
+                linux_client = self.get_remote_client(
                     server_or_ip=floating_ip.ip,
                     username=self.image_utils.ssh_user(self.image_ref),
-                    private_key=self.keypair.private)
+                    private_key=self.keypair.private_key)
+                linux_client.validate_authentication()
             except Exception:
                 LOG.exception('ssh to server failed')
                 self._log_console_output()