Remove lockutils fixture from this library
Remove lockutils fixture from this library

The module oslo.test.fixture.lockutils depends on another oslo
library, introducing a circular dependency between it and this
test library. We will distribute the lockutils fixtures as part
of the other library.

Change-Id: I46c9d14a6a5583f36062e72c8b4f729afe3dca6c

openstack/oslotest,openstack/oslotest