btl/openib: fix a typo

cmr=v1.8.3:reviewer=miked
btl/openib: fix use of mca_btl_openib_component.default_recv_qps

- do not have mca_btl_openib_component.default_recv_qps point to the stack
- do not reset mca_btl_openib_component.default_recv_qps in btl_openib_component_open

cmr=v1.8.3:reviewer=miked