nfs: fix docker_exec_cmd_nfs default value
nfs: fix docker_exec_cmd_nfs default value

the default is not an array, default is empty.

Signed-off-by: Sébastien Han <62d754cc350e84d3b1c32ae79f976f5348e74a40@redhat.com>

ceph/ceph-ansible,travmi/ceph-ansible,fgal/ceph-ansible,ceph/ceph-ansible,travmi/ceph-ansible,jtaleric/ceph-ansible,jtaleric/ceph-ansible,font/ceph-ansible,font/ceph-ansible,fgal/ceph-ansible