io_commands.c, tcpforward.c, tcpforward_commands.c: In collect_*
functions, don't assert that info == NULL. It's info->next that
should be NULL.

Rev: src/channel_commands.c:1.7
Rev: src/combinators.c:1.5
Rev: src/connection_commands.c:1.6
Rev: src/io_commands.c:1.12
Rev: src/tcpforward.c:1.20
Rev: src/tcpforward_commands.c:1.3