devmapper: remove unnecessary variable in struct
devmapper: remove unnecessary variable in struct

dx9/convoy,dx9/convoy,medallia/convoy,aruneli/convoy,dx9/convoy,jinuxstyle/convoy,rancherio/volmgr,rancher/convoy,rancher/convoy,mehulsbhatt/convoy,rancherio/volmgr,rancherio/rancher-volume,rancher/rancher-volume,rancherio/volmgr,nickvanw/convoy,aruneli/convoy,moypray/convoy,rancher/convoy,moypray/convoy,jinuxstyle/convoy,rancherio/rancher-volume,medallia/convoy,moypray/convoy,nickvanw/convoy,jinuxstyle/convoy,aruneli/convoy,rancher/rancher-volume,rancherio/rancher-volume,medallia/convoy,nickvanw/convoy,rancher/rancher-volume,mehulsbhatt/convoy,mehulsbhatt/convoy