nsupdate: fix 'index out of range' error when no TTL answer is given (#7219)
* nsupdate: fix 'index out of range' error when no TTL answer is given
Fix a possible `list index out of range` when no answer is returned in the `ttl_changed` method
by applying the existing workaround for NS records to all record types.
Resolves#836
* fixup! nsupdate: fix 'index out of range' error when no TTL answer is given
(cherry picked from commit 208df2c9e6)
Co-authored-by: Silke Hofstra <silkeh@users.noreply.github.com>
