We were being too aggressive when deciding whether to write our NRPT rules
to the local registry key or the group policy registry key.
After once again reviewing the document which calls itself a spec
(see issue), it is clear that the presence of the DnsPolicyConfig subkey
is the important part, not the presence of values set in the DNSClient
subkey. Furthermore, a footnote indicates that the presence of
DnsPolicyConfig in the GPO key will always override its counterpart in
the local key. The implication of this is important: we may unconditionally
write our NRPT rules to the local key. We copy our rules to the policy
key only when it contains NRPT rules belonging to somebody other than us.
Fixes https://github.com/tailscale/corp/issues/19071
Signed-off-by: Aaron Klotz <aaron@tailscale.com>
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