IB/core: Set qp->real_qp before it may be accessed

real_qp should be initialized before ib_destroy_qp() is called.
ib_destroy_qp() may be called in the error flow if ib_create_qp_security()
failed.

Signed-off-by: Artemy Kovalyov <artemyko@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>