hosts.alpine.tmpl: rearrange the order of short and long hostnames

[dermotbradley]

Proposed Commit Message

hosts.alpine.tmpl: rearrange the order of short and long hostnames

The Alpine /etc/hosts template results in a file where the long form of
names (including localhost) come before the short form. This means that
when running tools like 'netstat' and 'ss' which convert IP address to
names that their output will show 'localhost.localdomain' rather than
'localhost.' This patch swaps the order of the short and long form names
so such utils will show the short form name.

It also removes several unnecessary IPv6-specific entries.

Additional Context

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

[holmanb]

Thanks for the PR @dermotbradley.

The FQDN should definitely be second.

I don't think removing the addresses should be an issue. I spot checked alpine 3.11 and edge, both have the following /etc/hosts value:

127.0.1.1	me
127.0.0.1	localhost localhost.localdomain
::1		localhost localhost.localdomain

A grep of the codebase shows that the alpine template is the only one to have those extra addresses and cloud-init doesn't seem to use them. Since they are unnecessary for common usage, I don't have any objections to this.

[dermotbradley]

A grep of the codebase shows that the alpine template is the only one to have those extra addresses and cloud-init doesn't seem to use them. Since they are unnecessary for common usage, I don't have any objections to this.

They used to also be present in the Debian template until they were removed last month by #1021.

These entries are only in the Alpine template as, at the time, I thought they were a good idea (I submitted the original Alpine support for cloud-init).

[TheRealFalcon]

Will merged once CI fix is merged.