Comment 36 for bug 1781286

Reviewed: https://review.opendev.org/686264
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=53bcf0b1eeb4d34cbbec6200026c9bac5921db97
Submitter: Zuul
Branch: stable/stein

commit 53bcf0b1eeb4d34cbbec6200026c9bac5921db97
Author: Matt Riedemann <email address hidden>
Date: Tue Oct 1 12:03:17 2019 -0400

    Handle get_host_availability_zone error during reschedule

    If a build fails and reschedules to a cell conductor which does
    not have access to the API DB, the call to get_host_availability_zone
    will fail with a CantStartEngineError because it's trying to do an
    "up-call" to the API DB for host aggregate info. The reschedule
    fails and the instance is stuck in BUILD status without a fault
    injected for determining what went wrong.

    This change simply handles the failure and cleans up so the instance
    is put into a terminal (ERROR) state.

    NOTE(mriedem): The fill_provider_mapping mock on the unit test is
    removed since that method did not exist in Stein, it was introduced
    in Train: I76f777e4f354b92c55dbd52a20039e504434b3a1

    Change-Id: I6bfa6fa767403fb936a6ae340b8687eb161732fc
    Partial-Bug: #1781286
    (cherry picked from commit 38fb7f82abd7fffc00ebc050ee5230f1137e76d8)
    (cherry picked from commit b5e6c389d733d4dbd94380add7e3fa6c4d1e3fa8)