Systematically update DNS Records when using external DNS

[f-trivino]

Benefit from the ipa dns-update-system-records --dry-run command to systematically update DNS records when using external DNS.

When using external DNS, FreeIPA does not automatically update the DNS records after a change in the topology. However, ansible-freeipa automation can rely on ipa dns-update-system-records --dry-run command to store content in a variable for further processing. The command with --dry-run displays the records that require updating. The same command with the --out option can store the content in a file, that can later be use by nsupdate for instance.

This is just a nice to have.