Allow disable_instance_snapshot to be set to True

[Giuseppe Petralia]

One of Bootstack customer would like to have instance snapshot creation disabled on their
environment.

This means we should be able to add in local_settings.py to LAUNCH_INSTANCE_DEFAULTS
disable_instance_snapshot = True

This is currently not allowed with xenial-queens charm-openstack-dashboard.

We are using openstack-dashboard version: 13.0.1 revision: 274 xenial-queens serie

[Ryan Beisner (1chb1n)]

This bug reads like a nice-to-have feature request. If this bug has more context to drive a higher level of importance than 'wishlist,' please clarify. Thank you.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/701755
Committed: https://git.openstack.org/cgit/openstack/charm-openstack-dashboard/commit/?id=03cb557fc8afc9526cd32d13b0fe7162f10d8c24
Submitter: Zuul
Branch: master

commit 03cb557fc8afc9526cd32d13b0fe7162f10d8c24
Author: Alex Kavanagh <email address hidden>
Date: Thu Jan 9 15:34:09 2020 +0000

    Add disable-instance-snapshot config item

    This patchset adds the disable-instance-snapshot config item that
    controls the "disable_instance_snapshot" dictionary item in the
    LAUNCH_INSTANCE_DEFAULTS setting in local_settings.py

    Change-Id: Ic15f60517ed8a7f67704b15f4b42baabe74f83c6
    Closes-Bug: #1818221