VMware VCDriver: the _init_host and period power sync take too long time when there are thousands VMs

[Feng Xi Yan]

When the nova compute service is starting, it will do a host_init, and this will result in initing instance one by one, by fetching VMs info one by one from vCenter. If there are thousands of VMs on OpenStack, there will be thousands of requests to vCenter, which is a big network burden.

This circumstance also happens when compute manager doing periodical power state syncing. If the power state syncing takes too long time, and too network bandwidth, it will block the ongoing normal VM deployment.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/255586

[OpenStack Infra (hudson-openstack)]

Change abandoned by Michael Still (<email address hidden>) on branch: master
Review: https://review.openstack.org/255586
Reason: This code hasn't been updated in a long time, and is in merge conflict. I am going to abandon this review, but feel free to restore it if you're still working on this.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Michael Still (<email address hidden>) on branch: master
Review: https://review.openstack.org/242006
Reason: This patch has been sitting unchanged for more than 12 weeks. I am therefore going to abandon it to keep the nova review queue sane. Please feel free to restore the change if you're still working on it.