BUG/MINOR: http-ana: fix NTLM response parsing again

Commit 9df188695f ("BUG/MEDIUM: http-ana: Handle NTLM messages correctly.")
tried to address an HTTP-reuse issue reported in github issue #511 by making
sure we properly detect extended NTLM responses, but made the match case-
sensitive while it's a token so it's case insensitive.

This should be backported to the same versions as the commit above.
diff --git a/src/http_ana.c b/src/http_ana.c
index d475cd2..79124e7 100644
--- a/src/http_ana.c
+++ b/src/http_ana.c
@@ -1824,7 +1824,7 @@
 		ctx.blk = NULL;
 		while (http_find_header(htx, hdr, &ctx, 0)) {
 			if ((ctx.value.len >= 9 && word_match(ctx.value.ptr, ctx.value.len, "Negotiate", 9)) ||
-			    (ctx.value.len >= 4 && !memcmp(ctx.value.ptr, "NTLM", 4))) {
+			    (ctx.value.len >= 4 && strncasecmp(ctx.value.ptr, "NTLM", 4) == 0)) {
 				sess->flags |= SESS_FL_PREFER_LAST;
 				srv_conn->flags |= CO_FL_PRIVATE;
 			}