It needs to clear qp context previous when init qp context.  Otherwise,
the newly created qp context residue has the contents of the qp context
before the uninstall, and the qp context content is disordered, causing
the task to fail.
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>