(PUP-2660) user: set the user should-value when generating ssh_authorized_keys

When purging authorized SSH keys, the user type generates ssh_authorized_keys
resources using eval_generate. The ensure property receives a should value of
"absent" so the keys are removed. However, those resources are non-functional
because the user property lacks a should value. The resource fails during
Provider::Ssh_authorized_keys::Parsed#flush.

Fixed by setting the appropriate user value for each generated key.
Merge remote-tracking branch 'ffrank/ticket/3.6.1/PUP-2660-keys-not-purged-missing-user' into stable

* ffrank/ticket/3.6.1/PUP-2660-keys-not-purged-missing-user:
  (PUP-2660) user: set the user should-value when generating ssh_authorized_keys
(PUP-2639) Change default timeout to 3 minutes

The 5 second timeout was selected assuming that the major use case would
be around a development workflow in which a user edits manifests on a
master and then immediately runs an agent to see the effect. It turns
out that this caused a lot of problems for a much more common and
impactful case of users updating to directory environments where they
ended up with excessive CPU usage. Nearly any value here is arbitrary
except 0 (purely development workflow) and unlimited (best choice for
production systems).

This makes the almost arbitrary decision that a 3 minute timeout will
create less confusion for upgrading users. It means that a development
workflow will require more restarts, however. :(
Merge pull request #2710 from zaphod42/feature/stable/pup-2639-increase-environment-timeout

(PUP-2639) Change default timeout to 3 minutes
Merge remote-tracking branch 'upstream/stable'

* upstream/stable:
  (PUP-2639) Change default timeout to 3 minutes
  (PUP-2660) user: set the user should-value when generating ssh_authorized_keys