add time to logging in unit tests
add time to logging in unit tests

It's quite difficult to debug unit test failures when you don't have
any idea when the log messages happened relative to each other. Update
the logging fixture so that we are actually writing out time into our
log messages.

Change-Id: I704792f10d77345246d528bd9abf2e0c46b6df72

citrix-openstack-build/oslo.versionedobjects,openstack/oslo.versionedobjects