Cleanup Daemon.verifyVolumesInfo() a bit
Cleanup Daemon.verifyVolumesInfo() a bit

vols.VolumesRW has been initialized so it can't be nil. Furthermore
it's ok to read a nil map.

Signed-off-by: Zefan Li <a8167b9d27aca9c6624754deb52c4c6420eded04@huawei.com>
(cherry picked from commit 8b4c0decfc6a3ef748a70c2f53d1351d5aa8ab64)

AdamOssenford/docker-pi,AdamOssenford/docker-pi,AdamOssenford/docker-pi