ceph_objectstore_tool: Rename generated binary to ceph-objectstore-tool

Signed-off-by: David Zafman <dzafman@redhat.com>
Merge pull request #3207 from ceph/wip-cot-rename

ceph_objectstore_tool: Rename generated binary to ceph-objectstore-tool

Reviewed-by: Loic Dachary <ldachary@redhat.com>