When we encounter a source we cannot resolve, we skipped the whole rule,
even if some of the srcs could be resolved. In this case, if we had one user
that exists and one that does not.
In the regular policy, we log this, and still let a rule be created from what
does exist, while in the SSH policy we did not.
This commit fixes it so the behaviour is the same.
Fixes#2863
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>