Add validation for volume_type of volume object

Add validation for volume_type of volume object

During copy_volume_to_image(), this tries to return
volume['volume_type'] attribute in a volume object, but
if the volume does not have a volume type, this would
trigger a db call which raise an 404 not found error.

Volume object should check volume_type_id at first and
then decide whether returning volume_type or None to
avoid VolumeTypeNotFound exception.

Also this change includes LOG.info messages fix to show
right behavior of copy_volume_to_image().

Change-Id: Id2372621962406282eece2bcbc56c242f9dff8a0
Closes-Bug: #1523362