Update pre_live_migration to take instance object

Update the pre_live_migration method in the compute api, compute manager,
and virt driver to take an instance object.  The update to the compute manager
call also happens to finish the conversion of
ensure_filtering_rules_for_instance in the virt driver API, as well.

Part of blueprint virt-objects

Change-Id: I2ddb1d72dbbd11e153f75171b3a4dc4f87ca3972
Merge "Update pre_live_migration to take instance object"