source: Force OpenStack when it is only option (#2045)

Running on OpenStack Ironic was broken in 1efa8a0a0,
which prevented a system configured to run on only
Openstack from actually running this ds. This change
also prevents the kernel commandline definition from
working. This change was required to prevent
unnecessarily probing OpenStack on Ec2, and is
therefore still required.

This commit reverts an earlier attempt[1][2] to
automatically detect OpenStack, due to regression
it caused. Additionally, this change allows a
system that defines a datasource list containing
only [OpenStack] or [OpenStack, None] to attempt
running on OpenStack, overriding ds_detect(). A
datasource list that defines [OpenStack, None]
still falls back to DataSourceNone if OpenStack
fails to reach the IMDS.

This change also lays groundwork for the following
future work:

1. Add support for other datasources
2. Also override datasource checking when the kernel
   command line defines a datasource. This work needs
   to be done manually to support non-systemd systems.

Besides forcing OpenStack to run when it is the only
datasource in the datasource list, this commit also:

[1] 0220295 (it breaks some use cases)
[2] 29faf66 (no longer used)

LP: #2008727

0 files changed, 0 insertions, 0 deletions