Bring configuration in line with the latest Cloud init verison. Tested under 20.1.
Mainly done due to `debconf_selections` not working with the old syntac.
See the `debconf_selections` item under https://cloudinit.readthedocs.io/en/latest/topics/modules.html#apt-configure
Changes include:
- reboot when apt deems it necessary,
- define update and upgrade with the package syntax,
- bring apt sources and keys inline with apt syntax and
- dynamically get the right release by using the var '$RELEASE'.
[ci skip]
This cloudinit script had become outdated.
Changed 4 things:
- docker repository had moved
- use current docker gpg key
- use current dokku gpg key
- move over to ubuntu focal LTS 20.20
While the latest packages may continue to work on other releases, we will no longer officially support these releases, nor will we distribute packages.
