Fix vd_path and error in spa_vdev_remove()

Fix vd_path and error in spa_vdev_remove()

Make a local copy of the vd_path and preserve the removal error
for use in spa_history_log_internal().  This is required because
after spa_vdev_exit() there is nothing preventing the vdev state
from changing.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Signed-off-by: Igor Kozhukhov <igor@dilos.org>
Closes #8522