General fixups discovered by checking errors

There was a lot of tests that actually threw a lot of errors and that did
not pass all the way because we didnt check everything. This commit should
fix all of these cases.

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

.golangci.yaml

@@ -30,6 +30,7 @@ linters:
     - exhaustruct
     - nolintlint
     - musttag # causes issues with imported libs
+    - depguard
 
     # deprecated
     - structcheck # replaced by unused