Comment 2 for bug 1471022

So it does appear that this a result of the openvswitch-switch service taking a while to startup on boot/reboot. I have added some retry logic to nova-compute and it appears that openvswitch is taking around 80s to start:

neutron-ovs-cleanup start/pre-start, process 3055
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 1s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 3s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 3s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 5s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 5s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 7s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 7s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 9s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 9s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 11s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 11s
neutron-ovs-cleanup start/pre-start, process 3055
Attempting to start neutron-ovs-cleanup
start: Job is already running: neutron-ovs-cleanup
Recheck neutron-ovs-cleanup status in 13s
neutron-ovs-cleanup start/running
2015-07-03 17:51:40.660 15690 DEBUG nova.servicegroup.api [-] ServiceGroup driver defined as an instance of db __new__ /usr/lib/python2.7/dist-packages/nova/servicegroup/api.py:65
2015-07-03 17:51:43.053 15690 INFO nova.openstack.common.periodic_task [-] Skipping periodic task _periodic_update_dns because its interval is negative
2015-07-03 17:51:44.320 15690 DEBUG stevedore.extension [-] found extension EntryPoint.parse('file = nova.image.download.file') _load_plugins /usr/lib/python2.7/dist-packages/stevedore/extension.py:156
2015-07-03 17:51:44.602 15690 DEBUG stevedore.extension [-] found extension EntryPoint.parse('file = nova.image.download.file') _load_plugins /usr/lib/python2.7/dist-packages/stevedore/extension.py:156
2015-07-03 17:51:44.603 15690 INFO nova.virt.driver [-] Loading compute driver 'libvirt.LibvirtDriver'

I'll have an SRU patch up shortlty