Restore compatibility with curl < 7.16.2

Follows-up 58f71c7e9eca, which assumed that the CURLOPT_CONNECTTIMEOUT_MS
constant was defined.

Bug: 58178
Change-Id: Id31a3ec56e4c7cac7d3edb2653c87be467d1a471
(cherry picked from commit 33bc02fad1b73a06e402ea0d19d951b60ca30256)