swift-related code needs refactoring

[Pavlo Shchelokovskyy]

currently 3 places in Ironic use swift-related actions:
- ilo drivers uses SwiftAPI object from common/swift.py for virtual media boot
- conductor manager uses SwiftAPI object to store configdrive
- glance_service that creates temp_urls for glance images stored in Swift and _does not use_ SwiftAPI object

It would be beneficial to centralize Swift-related code in common/swift.py.

Moreover, we could reduce entanglement between service configs and do not need to have the "swift_temp_url_key" set in both swift's and Ironic's configs (that is used only for glance image_service), as Ironic can discover it from account headers when using proper swiftclient instead of functions from swift_utils, same as ILO drivers are doing already.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/352289

[OpenStack Infra (hudson-openstack)]

Related fix proposed to branch: master
Review: https://review.openstack.org/368782

[OpenStack Infra (hudson-openstack)]

Change abandoned by Galyna Zholtkevych (<email address hidden>) on branch: master
Review: https://review.openstack.org/368782
Reason: not needed as soon as it tested alone

[OpenStack Infra (hudson-openstack)]

Change abandoned by Galyna Zholtkevych (<email address hidden>) on branch: master
Review: https://review.openstack.org/352289
Reason: since this patch is split into two logically indepependent paths

[OpenStack Infra (hudson-openstack)]

Change abandoned by Vladyslav Drok (<email address hidden>) on branch: master
Review: https://review.openstack.org/410767
Reason: Pavlo's patches take care of this, it can be abandoned.

[Vladyslav Drok (vdrok)]

There is only one patch left on review, and it does not fix the problem described here. I'm setting the bug back to triaged and unassigning, as Galyna does not work on ironic anymore.

[Pavlo Shchelokovskyy (pshchelo)]

I'd say that this patch https://review.openstack.org/#/c/526429/ kind of solves most of the problems I intended to be solved when reporting this bug, at least the config options entanglement.

Refactoring for glance_service to use SwiftAPI can still be beneficial though.

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Julia Kreger <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/ironic/+/410764