Fix failing copy_image flow init in wallaby

[Abhishek Kekane]

The new networkx requirement apparently causes us to fail the test_init_copy_flow_as_non_owner test because a None value can not be added to the flow graph. This just mocks out the glance_store call
that is failing to get the staging store to avoid us choking there so we can proceed. We are just testing get_flow so we never use it anyway.

This issue was fixed in Xena but now we realised that it is causing problem in Wallaby as well.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/wallaby
Review: https://review.opendev.org/c/openstack/glance/+/826975

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/glance/+/826975
Committed: https://opendev.org/openstack/glance/commit/b1d635c287f950b15df207455d64d97228963e5f
Submitter: "Zuul (22348)"
Branch: stable/wallaby

commit b1d635c287f950b15df207455d64d97228963e5f
Author: Dan Smith <email address hidden>
Date: Wed Aug 4 08:18:55 2021 -0700

    Fix failing copy_image flow init

    The new networkx requirement apparently causes us to fail the
    test_init_copy_flow_as_non_owner test because a None value can not be
    added to the flow graph. This just mocks out the glance_store call
    that is failing to get the staging store to avoid us choking there
    so we can proceed. We are just testing get_flow so we never use it
    anyway.

    Closes-Bug: #1959361

    Change-Id: I6fcb14ad240105ed0b1b9086c6c6c95034b4dd42
    (cherry picked from commit ded8ecf3828fa9afd7382f8ba850505ae0541e2c)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/glance 22.1.1 release.