fixes #20001 - Allow access to interface fqdn from snippets

This allows snippets to access an interface's `fqdn` and `shortname`.

Fixes #19991 - Add network6 to nic model

This adds the method `network6`, delegated to the `subnet6` relation.
Because the `delegate` methods does not support completely renaming a
method, I use a combination of delegate and alias. I updated the
definition for `network` (the v4 equivalent) to be consistent.

Fixes #19728 - set admin user in rake console

Fixes #19631 - ComputeResource with KeyPair can be removed

The concern for removing the compute resources with keypairs was trying
to destroy the compute resource too early. Also, this deletion already
happened because of the has_one :dependency => :destroy relation...

Fixes #19762 - upgrade to rubocop 0.49.1

Fixes #15861 - increase size of audited_changes column

In mysql text type is limited to 64K, while in psql
there's no limit. Changeing type to MEDIUMTEXT,
which limited to 16MB, should solve this issue in mysql

Fixes #19700 - update rubocop rules

The following changes have been made:

- Performance/RedundantMerge:
changes lines such as:
```not_found_message.merge! :message => options```
to:
```not_found_message[:message] = options```

- converts str.match() to str =~ ()...

Fixes #19612 - CVE-2017-7505 don't expose admin to taxed users

Fixes #19632 - changed shim and grub1 PXE names

Fixes #19459 - improve vm boot failure feedback

To be able to override the wait for vm ready we need to move
it to compute resource definition. Also improve Openstack one