SmartOS: run salt minion in an audit context

This fixes an issue @njones11 was having with
multiple cron.present states.

"crontab -l <username>" would fail, so the temp file
would be empty, a given cronjob would go in
and then the "su - <username> crontab <temp file>" would
succeed.

This evaded debugging attempts because if you invoked the salt
minion manually from a login shell, an audit context would
already exist and the "crontab -l <username>" would succeed.

The hint was a message in the debug log of:
[ERROR   ] Command 'crontab -l legion' failed with return code: 1
[ERROR   ] stderr: crontab: The audit context for your shell has not
been set.

We explicitly set up an audit context when launching the salt minion
which allows "crontab -l <username>" to succeed.

This may fix other issues and something similar
should perhaps be applied to pkg/smartos/salt-minion.xml

"5417" was chosen arbitrarily
Merge pull request #13573 from nshalman/smartos-audit-context

SmartOS: run salt minion in an audit context