The strict adherance to RFC7323 (D27148) requires the server to take
into consideration, if it will be sending out a TSopt in the SYN,ACK.
Retaining the TF_RCVD_TSTMP would otherwise later indicate the
successful negotiation of the TSopt - even when the session was set up
without TS support.
See also bug 253576
MFC after: 3 days