Revert "Ensure system_cfg read before ds net config on Oracle (#1174)"

[TheRealFalcon]

Proposed Commit Message

This reverts commit b306633fd17e5ba0173ad3c41add59cb11884757.

While this ultimately seems like a better solution, currently the
file /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg exists on
all Oracle launched instances which will prevent networking from
being properly initialized.

Additional Context

#1174
https://bugs.launchpad.net/cloud-init/+bug/1956788

Test Steps

Checklist:

• My code follows the process laid out in the documentation
• I have updated or added any unit tests accordingly
• I have updated or added any documentation accordingly

[TheRealFalcon]

@smoser or @OddBloke , do either of you have any context as to why Oracle images have the file /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg, whose contents disable networking? The ordering of network_config_sources made it so that this file hasn't been respected anyway. I'm curious if we can request that this file be removed.

[TheRealFalcon]

I built a deb and tested that tests/integration_tests/modules/test_combined.py runs successfully. Without this revert, we would not be able to connect to the instance.

[blackboxsw]

LGTM revert is clean revert here to what was already released and functional on Oracle.