[SSSD] [sssd PR#682][opened] DYNDNS: Drop support for legacy NSUPDATE

[thalman]

   URL: https://github.com/SSSD/sssd/pull/682
Author: thalman
 Title: #682: DYNDNS: Drop support for legacy NSUPDATE
Action: opened

PR body:
"""
We should drop support for legacy versions of NSUPDATE that doesn't
support 'realm' option. The option 'realm' was added in
BIND 9.8.0a1.

Resolves:
https://pagure.io/SSSD/sssd/issue/2817
"""

To pull the PR as Git branch:
git remote add ghsssd https://github.com/SSSD/sssd
git fetch ghsssd pull/682/head:pr682
git checkout pr682