Fix regression in passive-socket-pair establishment that was
introduced with the convert-to-active-on-timeout functionality.

In short, the passive client socket still wants to inherit SO_PASSIVE
from the parent listen, as it will only ever be created from an
SO_PASSIVE listen socket, and it needs to be marked
SO_PASSIVE/INP_PASSIVE before tcp_do_segment() is called to avoid
unwanted transmissions.