Use jsonutils from oslo.serialization

Rather than sync'ing with oslo-incubator, let's use the library
oslo.serialization instead.
We can't remove jsonutils under keystone/openstack/common/
because it's still used by other common functions.

Change-Id: Ic3e8d621616dd1cf14ac1446405896f2dc61288b
Merge "Use jsonutils from oslo.serialization"