Fix base object serialization checks
Fix base object serialization checks

We're missing unicode and long types in python 2 and bytes in python 3
here. These don't need to be serialized but will currently emit a
warning log when we hit this path. Add these types (via six so we're
compatible).

Change-Id: Ifb0fba3a82d7b24c25893ba258c74a66630617d9

pshchelo/ironic,SauloAislan/ironic,NaohiroTamura/ironic,NaohiroTamura/ironic,openstack/ironic,pshchelo/ironic,SauloAislan/ironic,openstack/ironic