connect: fix race condition with happy eyeballs timeout

The timer should be started after conn->connecttime is set. Otherwise
the timer could expire without this condition being true:

    /* should we try another protocol family? */
    if(i == 0 && conn->tempaddr[1] == NULL &&
      curlx_tvdiff(now, conn->connecttime) >= HAPPY_EYEBALLS_TIMEOUT) {

Ref: #1928