socket_connect sets O_NONBLOCK before connect and bounds the attempt with
poll(timeout); new connect_timeout_ms param (0=DEFAULT_CONNECT_TIMEOUT_MS);
all 5 callers updated (ha.c x3, client.c, xcectx.c). Revalidation Trigger:
shared netio helper signature changed. Broad build links all components;
xcelib_test 278/0, controller_unit_test 194/0. 1.4/1.5 unit tests satisfied
by the TDD output of 1.2/1.3 (test_slowlane.c, test_netio_bounded_connect.c).
