BUG/MINOR: mux-h1: Fix processing of "Connection: " header on outgoing messages

in h1_process_output(), before formatting the headers, we need to find and check
the "Connection: " header to update the connection mode. But, the context used
to do so was not correctly initialized. We must explicitly set ctx.value to NULL
to be sure to rescan the current header.

src/mux_h1.c

@@ -1219,6 +1219,7 @@ static size_t h1_process_output(struct h1c *h1c, struct buffer *buf, size_t coun
 					 * right one.
 					 */
 					ctx.blk = blk;
+					ctx.value = ist(NULL);
 					if (http_find_header(chn_htx, n, &ctx, 1))
 						goto process_hdr;
 					h1_process_conn_mode(h1s, h1m, NULL, &v);