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/ssl_sock.c b/src/ssl_sock.c
index e8e0eab..6ffdf4d 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -7224,7 +7224,7 @@
 static int cli_io_handler_tlskeys_files(struct appctx *appctx)
 {
 	struct show_keys_ctx *ctx = appctx->svcctx;
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 
 	switch (ctx->state) {
 	case SHOW_KEYS_INIT:
@@ -7503,7 +7503,7 @@
 	struct buffer *trash = alloc_trash_chunk();
 	struct buffer *tmp = NULL;
 	struct ebmb_node *node;
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 	struct certificate_ocsp *ocsp = NULL;
 	BIO *bio = NULL;
 	int write = -1;
@@ -7639,7 +7639,7 @@
 static int cli_io_handler_show_providers(struct appctx *appctx)
 {
 	struct buffer *trash = get_trash_chunk();
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 	struct list provider_names;
 	struct provider_name *name;
 
@@ -7770,7 +7770,7 @@
 {
 	struct buffer *trash = alloc_trash_chunk();
 	struct certificate_ocsp *ocsp = appctx->svcctx;
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 
 	if (trash == NULL)
 		return 1;