MRP-881 ptlrpc: fix put export for hp request

Fix for ASSERTION(cfs_list_empty(&exp->exp_hp_rpcs)) failed.

The root cause is in target_handle_connect()
        if (req->rq_export != NULL)
                class_export_put(req->rq_export);

        /* request takes one export refcount */
        req->rq_export = class_export_get(export);

For previous export it release export reference, but
rq_exp_list still in exp_hp_rpcs queue, after connect
requests became hp requsts. ptltpc_handle_request put last
reference for export and export go to zombie list with non
empty exp_hp_rpcs.
This patch add rq_exp_list move to new export at
target_handle_connect(), and cleanup for MRP-649.

Signed-off-by: Alexander Boyko <alexander_boyko@xyratex.com>
Change-Id: Ie159bd7978d77d9c64f4e54f178423eab37d0765
Reviewed-on: http://morpheus.xyus.xyratex.com:8443/gerrit/299
Tested-by: Jenkins
Tested-by: Alexander Lezhoev <Alexander_Lezhoev@xyratex.com>
Reviewed-by: Andriy Skulysh <Andriy_Skulysh@xyratex.com>
Reviewed-by: Vitaly Fertman <Vitaly_Fertman@xyratex.com>