Add custom sshd config instead of changing value

The 60-cloudimg-settings.conf exist on new LXD with
"PasswordAuthentication no" so we need to define our own config file.

src/tests/functional/tests/configure.py

@@ -22,8 +22,7 @@ def set_ssh_password_access_on_backup_host():
     """Configure ssh access with password on backup host."""
     backup_host_unit = _get_unit("backup-host")
     command = (
-        "sed -i 's/PasswordAuthentication no/PasswordAuthentication yes/' "
-        "/etc/ssh/sshd_config && "
+        'echo "PasswordAuthentication yes" > 01-test-settings.conf &&'
         "service sshd reload"
     )
     result = zaza.model.run_on_unit(backup_host_unit.name, command, timeout=15)