Stop using heat-admin as ansible_ssh_user

We use tripleo-admin when running config-downloaded
playbooks with overcloud deploy, update and upgrade.
We used to generate the inventory with tripleo-admin
as the default ansible_ssh_user. After we moved to
generate inventory with node provision the default
ansible_ssh_user has changed to heat-admin. This
patch drops heat-admin user completely as we don't
need it anymore.

Depends-On: https://review.opendev.org/c/openstack/tripleo-quickstart/+/849807
Change-Id: I51c3d6af40b6b268bb8e3fb26fe4c2833254549f

tripleoclient/tests/v1/overcloud_deploy/test_overcloud_deploy.py

@@ -1549,7 +1549,7 @@ class TestDeployOvercloud(fakes.TestDeployOvercloud):
                     ],
                     'baremetal_deployed_path': env_path,
                     'ssh_public_keys': 'sekrit',
-                    'ssh_user_name': 'heat-admin',
+                    'ssh_user_name': 'tripleo-admin',
                     'ssh_private_key_file': self.tmp_dir.join('id_rsa.pub'),
                     'manage_network_ports': True,
                     'configure_networking': False,

tripleoclient/tests/v2/overcloud_node/test_overcloud_node.py

@@ -479,7 +479,7 @@ class TestProvisionNode(fakes.TestOvercloudNode):
                 ],
                 'baremetal_deployed_path': mock.ANY,
                 'ssh_public_keys': 'I am a key',
-                'ssh_user_name': 'heat-admin',
+                'ssh_user_name': 'tripleo-admin',
                 'ssh_private_key_file': key_file_name,
                 'node_timeout': 3600,
                 'concurrency': 20,

tripleoclient/v1/overcloud_admin.py

@@ -44,7 +44,7 @@ class Authorize(command.Command):
 
         parser.add_argument(
             '--overcloud-ssh-user',
-            default='heat-admin',
+            default='tripleo-admin',
             help=_('User for ssh access to overcloud nodes')
         )
         parser.add_argument(

tripleoclient/v1/overcloud_deploy.py

@@ -626,7 +626,7 @@ class DeployOvercloud(command.Command):
         )
         parser.add_argument(
             '--overcloud-ssh-user',
-            default='heat-admin',
+            default='tripleo-admin',
             help=_('User for ssh access to overcloud nodes')
         )
         parser.add_argument(

tripleoclient/v2/overcloud_node.py

@@ -246,7 +246,7 @@ class ProvisionNode(command.Command):
                             default=utils.env('OVERCLOUD_STACK_NAME',
                                               default='overcloud'))
         parser.add_argument('--overcloud-ssh-user',
-                            default='heat-admin',
+                            default='tripleo-admin',
                             help=_('User for SSH access to newly deployed '
                                    'nodes'))
         parser.add_argument('--overcloud-ssh-key',