fixup! Move ProxyFinder.checkForUpdates into request path

Move check of `pf.fetcher == nil` outside the handler.

Addresses: samuong#16 (comment)

proxyfinder.go

@@ -33,10 +33,12 @@ func NewProxyFinder(pacurl string, wrapper *PACWrapper) *ProxyFinder {
 }
 
 func (pf *ProxyFinder) WrapHandler(next http.Handler) http.Handler {
+	// If we don't have a fetcher, don't wrap the handler as there's nothing to do.
+	if pf.fetcher == nil {
+		return next
+	}
 	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
-		if pf.fetcher != nil {
-			pf.checkForUpdates()
-		}
+		pf.checkForUpdates()
 		next.ServeHTTP(w, req)
 	})
 }