BUG/MINOR: fix typo in processing of http-send-name-header

I downloaded version 1.4.19 this morning. While merging the code changes
to a custom build that we have here for our project I noticed a typo in
'session.c', in the new code for inserting the server name in the HTTP
header. The fix that I did is shown in the patch below.

[WT: the bug is harmless, it is only suboptimal]
1 file changed