CLEANUP: applet: remove the unneeded appctx->owner

This one is the pointer to the conn_stream which is always in the
endpoint that is always present in the appctx, thus it's not needed.
This patch removes it and replaces it with appctx_cs() instead. A
few occurences that were using __cs_strm(appctx->owner) were moved
directly to appctx_strm() which does the equivalent.
diff --git a/src/map.c b/src/map.c
index dea9bcd..89bbd9e 100644
--- a/src/map.c
+++ b/src/map.c
@@ -345,7 +345,7 @@
 static int cli_io_handler_pat_list(struct appctx *appctx)
 {
 	struct show_map_ctx *ctx = appctx->svcctx;
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 	struct pat_ref_elt *elt;
 
 	if (unlikely(cs_ic(cs)->flags & (CF_WRITE_ERROR|CF_SHUTW))) {
@@ -417,7 +417,7 @@
 static int cli_io_handler_pats_list(struct appctx *appctx)
 {
 	struct show_map_ctx *ctx = appctx->svcctx;
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 
 	switch (ctx->state) {
 	case STATE_INIT:
@@ -480,7 +480,7 @@
 static int cli_io_handler_map_lookup(struct appctx *appctx)
 {
 	struct show_map_ctx *ctx = appctx->svcctx;
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 	struct sample sample;
 	struct pattern *pat;
 	int match_method;
@@ -1030,7 +1030,7 @@
 
 	if (!finished) {
 		/* let's come back later */
-		cs_rx_endp_more(appctx->owner);
+		cs_rx_endp_more(appctx_cs(appctx));
 		return 0;
 	}
 	return 1;