BUG/MINOR: rhttp: fix incorrect dst/dst_port values

BUG/MINOR: rhttp: fix incorrect dst/dst_port values

With a @rhttp server, connect is not possible, transfer is only possible
via idle connection reuse. The server does not have any network address.

Thus, it is unnecessary to allocate the stream destination address prior
to connection reuse. This patch adjusts this by fixing
alloc_dst_address() to take this into account.

Prior to this patch, alloc_dst_address() would incorrectly assimilate a
@rhttp server with a transparent proxy mode. Thus stream destination
address would be copied from the destination address. Connection adress
would then be rewrote with this incorrect value. This did not impact
connect or reuse as destination addr is only used in idle conn hash
calculation for transparent servers. However, it causes incorrect values
for dst/dst_port samples.

This should be backported up to 2.9.