Reload tests broken in Py3

We have removed ssl support [1] this cycle which results in removing some ssl related config options, but we didn't removed all of its usage and two config options 'key_file' and 'cert_file' are still used in reload functionality [2] which is causing error when SIGHUP is sent to parent process and results in termination due to error and childs remaining stale.

If I comment/remove those two options from [2] then SIGHUP works just fine.

[1] https://review.opendev.org/#/c/697969/5/glance/common/wsgi.py
[2] https://github.com/openstack/glance/blob/master/glance/common/utils.py (L560, L561, L562)

I have verified the same by adding new store to enabled_backends config option and it is crating the new store (file) as well as adding image to this newly created store.

Fix proposed to branch: master
Review: https://review.opendev.org/713076

Reviewed: https://review.opendev.org/713076
Committed: https://git.openstack.org/cgit/openstack/glance/commit/?id=30ece7aa28ce8bef1bfe6d4ac68485e6b980f955
Submitter: Zuul
Branch: master

commit 30ece7aa28ce8bef1bfe6d4ac68485e6b980f955
Author: Khuong Luu <email address hidden>
Date: Fri Mar 13 14:54:54 2020 -0700

    Remove usages of SSL related config options in utils

    SSL support was removed by [1] which resulted in removal of some
    SSL related config options, but two config options 'key_file' and
    'cert_file' are still used in utils.stash_conf_values() which is called
    in reload functionality. When SIGHUP is sent to the parent process,
    this usage causes it to crash and its children processes become orphaned,
    which then causes the reload test to be stale (fail).

    This change also includes:
    - Remove 2 attributes and the decorator that help to skip this test
      (self.diable, self.disabled_message, and @skip_if_disabled)

    [1] https://review.opendev.org/#/c/697969/5/glance/common/wsgi.py

    Change-Id: I361c9d0b53a67b1cc60f0f3012e22accdcc46055
    Closes-Bug: #1855708

This issue was fixed in the openstack/glance 20.0.0.0b3 development milestone.

Reviewed: https://review.opendev.org/713720
Committed: https://git.openstack.org/cgit/openstack/glance/commit/?id=f3cbe90b3eab1f1952798937f177f23c4ef34e17
Submitter: Zuul
Branch: stable/train

commit f3cbe90b3eab1f1952798937f177f23c4ef34e17
Author: Erno Kuvaja <email address hidden>
Date: Wed Mar 18 19:20:10 2020 +0000

    Fix reloading under PY3

    This is not direct backport of Ussuri fix
    I361c9d0b53a67b1cc60f0f3012e22accdcc46055 but rather
    adaptation of it to facilitate SSL/TLS termination under
    py27.

    Co-Authored-By: Khuong Luu <email address hidden>

    Change-Id: Ifd25ed15211ebc864f3a61558834bb1dae16a062
    Closes-Bug: #1855708