ceph_objectstore_tool: Clean-up unused struct_ver in tool's metadata section

Exported struct_ver not used by write_info() or write_pg()

Signed-off-by: David Zafman <dzafman@redhat.com>
ceph_objectstore_tool: Prevent tool from transitioning struct_v on rm-past-intervals

Signed-off-by: David Zafman <dzafman@redhat.com>