This simply moves the pre_live_migration start notification
back to the start of the method before creating new volume
attachments. While in here, the list of bdms are passed to
the notify_about_instance_action method so if
[notifications]/bdms_in_notifications is True we don't have
to pull them out of the database again for each versioned
notification.
Conflicts in nova/compute/manager.py due to absence of comment from
f0b9d5204f.
Change-Id: I372eddb9e356b02328f937917a856bc631691f53
Partial-Bug: #1763051
(cherry picked from commit 7a2228142b)
(cherry picked from commit ae2da62955)
6b065dad80