Revert the pre-computed deadline approach. A successful TCP connect is
forward movement: the server is responsive. Giving banner+login a fresh
timeout window after connect avoids false verification failures on
slow-but-working servers. Worst case is 2*timeout total, which is still
bounded (not indefinite) and a safe trade-off vs. the risk of starving
the FTP handshake with leftover time from a slow connect.
Co-authored-by: Dylan Ayrey <[email protected]>