Update XRCD destroy flow to allow command failure.

Fixes: 28ad5f65 ("RDMA: Move XRCD to be under ib_core responsibility")
Link: https://lore.kernel.org/r/20200907120921.476363-8-leon@kernel.orgSigned-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>