Double-free of encryption wrapping key due to invalid pool properties

This commits fixes a double-free in zfs_ioc_pool_create() triggered by
specifying an unsupported combination of properties when creating a pool
with encryption enabled.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes #8791