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]
diff --git a/src/session.c b/src/session.c
index d87813e..e5b76eb 100644
--- a/src/session.c
+++ b/src/session.c
@@ -1888,7 +1888,7 @@
 
 		/* Now we can add the server name to a header (if requested) */
 		/* check for HTTP mode and proxy server_name_hdr_name != NULL */
-		if ((s->flags && SN_BE_ASSIGNED) &&
+		if ((s->flags & SN_BE_ASSIGNED) &&
 			(s->be->mode == PR_MODE_HTTP) &&
 			(s->be->server_id_hdr_name != NULL)) {