Make nova.virt.fake.FakeDriver useable in integration testing

With this change nova.virt.fake.FakeDriver can be used for scale testing
using devstack. By setting 'compute_driver = nova.virt.fake.FakeDriver'
in nova.conf and disabiling quota and other limits, we can load up nova
to think it is running 1000's of instances.  This particular scenario is
analagous to how the baremetal driver will work (one machine managing
100's to 1000's of instances).

Make nova.virt.fake.FakeDriver use CONF.host for hostname.

Change-Id: I731ca2968176b4e39dd2fe7fc99f479cc568398b
Merge "Make nova.virt.fake.FakeDriver useable in integration testing"