Moves populate retry logic to the scheduler utils

This change moves the _post_select_populate_filter_properties
to scheduler utils. It will be needed on conductor when we move
prep_resize code from scheduler to conductor.

Partially implements bp cold-migrations-to-conductor

Change-Id: Ifed70b60a3fe178bd39eec98615c0a76ceb33cc6
Changes ComputeTaskManager class to inherit base.Base

This is going to be needed for all migrations to conductor tasks
in order to get db access. We patch it separately to reduce
conflicts.

Partially implements bp cold-migrations-to-conductor

Change-Id: Icd686d373472498ed77f3133f655454aa035ae43
Merge "Moves populate retry logic to the scheduler utils"
Merge "Changes ComputeTaskManager class to inherit base.Base"
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp