all: fix golangci-lint errors

These erroneously blocked a recent PR, which I fixed by simply
re-running CI. But we might as well fix them anyway.
These are mostly `printf` to `print` and a couple of `!=` to `!Equal()`

Updates #cleanup

Signed-off-by: Will Norris <will@tailscale.com>

net/tshttpproxy/tshttpproxy_synology.go

@@ -47,7 +47,7 @@ func synologyProxyFromConfigCached(req *http.Request) (*url.URL, error) {
 	var err error
 	modtime := mtime(synologyProxyConfigPath)
 
-	if modtime != cache.updated {
+	if !modtime.Equal(cache.updated) {
 		cache.httpProxy, cache.httpsProxy, err = synologyProxiesFromConfig()
 		cache.updated = modtime
 	}