Documented --storage-opt=[] option in cli reference page. Content taken
from:
daemon/graphdriver/devmapper/README.md
Signed-off-by: Michal Minar <miminar@redhat.com>
Docker-DCO-1.1-Signed-off-by: Michal Minar <miminar@redhat.com> (github: SvenDowideit)
Upstream-commit: 716e639748
Component: cli