storage: volStorageBackendRBDRefreshVolInfo: refactor
storage: volStorageBackendRBDRefreshVolInfo: refactor

use the ret variable for return value

Signed-off-by: Yi Li <55e7333d41158bbb5c693ad611d1d73461adffca@winhong.com>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

zippy2/libvirt,olafhering/libvirt,crobinso/libvirt,jfehlig/libvirt,libvirt/libvirt,olafhering/libvirt,nertpinx/libvirt,zippy2/libvirt,nertpinx/libvirt,crobinso/libvirt,olafhering/libvirt,nertpinx/libvirt,olafhering/libvirt,crobinso/libvirt,libvirt/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt,nertpinx/libvirt,jfehlig/libvirt,zippy2/libvirt,jfehlig/libvirt,zippy2/libvirt,jfehlig/libvirt,libvirt/libvirt