plex: Stop after 10 redirects

Since the default CheckRedirect has been replaced with ours, we won't get the default protection of erroring after 10 redirects, so i've copied that back in from the std implementation

server/feature/plex/plex.go

@@ -345,6 +345,9 @@ var plexHTTPClient = &http.Client{
 		if len(via) == 0 {
 			return nil
 		}
+		if len(via) >= 10 {
+			return errors.New("stopped after 10 redirects")
+		}
 		if req.URL.Host != via[0].URL.Host {
 			req.Header.Del("X-Plex-Token")
 		}