lxd/db/storage/volumes: Modifies GetStorageVolumeNodeAddresses to detect volumes that are not bound to a single node
lxd/db/storage/volumes: Modifies GetStorageVolumeNodeAddresses to detect volumes that are not bound to a single node

Returns special error value in that case.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

hallyn/lxd,stgraber/lxd,atxwebs/lxd,lxc/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,stgraber/lxd,atxwebs/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,atxwebs/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,atxwebs/lxd