Dockerfile.openmpi ibverbs-providers version error

The hardcoded ibverbs version in Dockerfile.openmpi is no longer valid:

wget -nv $DEB_URL/r/rdma-core/${i}_${IBVERBS_VERSION}_amd64.deb ;     done
    ---> Running in dbbf022f3ef1
   http://http.us.debian.org/debian/pool/main/r/rdma-core/ibacm_19.0-1_amd64.deb:
   2018-09-20 06:04:08 ERROR 404: Not Found.

Similar to #245