libvirt: skip disk resize when resize_instance is False

The method finish_migration is called with an extra
parameter 'resize_instance'. It should be used to know
if it is necessary or not to resize the disks and so
call the method 'disk_resize'.

Change-Id: Ia5a9ad7994fa9abab7cf47d36468c46d97065991
Closes-Bug: #1298981
VMware: Remove references to ebs_root from spawn()

spawn() contained an important boolean called ebs_root. This was True
for any spawn which contained a block device mapping. This no longer
has any meaning, and was confusing. This change removes references to
ebs_root, instead using block_device_info directly.

N.B. The block device mapping behaviour of the VMware driver is still
not correct, but fixing it is not the purpose of this patch. This
patch simply makes the existing behaviour easier to see.

N.B. test_spawn_mask_block_device_info_password in test_vmops.py
assumes internal details of spawn in order to cause a failure after
emitting a log message. In moving the log message we need to update
the dance this test does to ensure that spawn fails after the log
message, but not before.

This change has been split out of
https://review.openstack.org/#/c/87002/, which was written by Shawn
Hartsock.

partial blueprint vmware-spawn-refactor

Co-authored-by: Shawn Hartsock <hartsocks@acm.org>
Change-Id: I11b355a6b53194bc9f85f542b54c9fbb9c061e04
scheduler sends select_destinations notifications

scheduler_run_instance sends start/end notifications so you can tell how
long it takes for the scheduler to do its work.

The new select_destinations does not send any such notifications.

To make the new code patch more consistent with the notifications in the
old code patch, this change adds in start/end notifications.

The notification docs should be updated to reflect this change.

DocImpact

Closes-Bug: #1359835

Change-Id: I9b3f6619823c57cbc21d714edd78527c0015b4f6
libvirt: support live migrations of instances with config drives

In case of shared storage, to allow an instance with a configdrive
to be migrated if we must store the configdrive into the same backend
as other disks.

Related to bug #1246201

Change-Id: I699f0746da03f7ef669d68665996c839d4d99ee4
Merge "scheduler sends select_destinations notifications"
Merge "libvirt: support live migrations of instances with config drives"
Merge "libvirt: skip disk resize when resize_instance is False"
Merge "VMware: Remove references to ebs_root from spawn()"