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
Merge "Multiple fixes to test_server_basic_ops"
Merge branch 'master' of https://github.com/openstack/tempest