Disable KVM at limestone (again)
Disable KVM at limestone (again)

There appears to be a kernel regression that is leading to KVM failures
again. This patch adds limestone to the exclusion list based on job
failures[1].

[1] http://logs.openstack.org/32/600332/3/check/octavia-v1-dsvm-scenario/ \
    467a1e6/logs/libvirt/qemu/instance-00000001.txt.gz

Change-Id: I356c32c27f9803226e9a449c2f81aa1d04af9671

openstack/octavia,openstack/octavia,openstack/octavia