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/flt_spoe.c b/src/flt_spoe.c
index f032e83..59db428 100644
--- a/src/flt_spoe.c
+++ b/src/flt_spoe.c
@@ -1137,7 +1137,7 @@
 static int
 spoe_send_frame(struct appctx *appctx, char *buf, size_t framesz)
 {
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 	int      ret;
 	uint32_t netint;
 
@@ -1163,7 +1163,7 @@
 static int
 spoe_recv_frame(struct appctx *appctx, char *buf, size_t framesz)
 {
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 	int      ret;
 	uint32_t netint;
 
@@ -1192,8 +1192,8 @@
 static int
 spoe_wakeup_appctx(struct appctx *appctx)
 {
-	cs_want_get(appctx->owner);
-	cs_rx_endp_more(appctx->owner);
+	cs_want_get(appctx_cs(appctx));
+	cs_rx_endp_more(appctx_cs(appctx));
 	appctx_wakeup(appctx);
 	return 1;
 }
@@ -1219,7 +1219,7 @@
 static void
 spoe_release_appctx(struct appctx *appctx)
 {
-	struct conn_stream  *cs          = appctx->owner;
+	struct conn_stream  *cs          = appctx_cs(appctx);
 	struct spoe_appctx  *spoe_appctx = SPOE_APPCTX(appctx);
 	struct spoe_agent   *agent;
 	struct spoe_context *ctx, *back;
@@ -1339,7 +1339,7 @@
 static int
 spoe_handle_connect_appctx(struct appctx *appctx)
 {
-	struct conn_stream *cs    = appctx->owner;
+	struct conn_stream *cs    = appctx_cs(appctx);
 	struct spoe_agent  *agent = SPOE_APPCTX(appctx)->agent;
 	char *frame, *buf;
 	int   ret;
@@ -1405,7 +1405,7 @@
 static int
 spoe_handle_connecting_appctx(struct appctx *appctx)
 {
-	struct conn_stream *cs     = appctx->owner;
+	struct conn_stream *cs     = appctx_cs(appctx);
 	struct spoe_agent  *agent  = SPOE_APPCTX(appctx)->agent;
 	char  *frame;
 	int    ret;
@@ -1650,7 +1650,7 @@
 
 	/* Do not forget to remove processed frame from the output buffer */
 	if (trash.data)
-		co_skip(cs_oc(appctx->owner), trash.data);
+		co_skip(cs_oc(appctx_cs(appctx)), trash.data);
   end:
 	return ret;
 }
@@ -1658,7 +1658,7 @@
 static int
 spoe_handle_processing_appctx(struct appctx *appctx)
 {
-	struct conn_stream      *cs    = appctx->owner;
+	struct conn_stream      *cs    = appctx_cs(appctx);
 	struct server           *srv   = objt_server(__cs_strm(cs)->target);
 	struct spoe_agent       *agent = SPOE_APPCTX(appctx)->agent;
 	int ret, skip_sending = 0, skip_receiving = 0, active_s = 0, active_r = 0, close_asap = 0;
@@ -1781,7 +1781,7 @@
 static int
 spoe_handle_disconnect_appctx(struct appctx *appctx)
 {
-	struct conn_stream *cs    = appctx->owner;
+	struct conn_stream *cs    = appctx_cs(appctx);
 	struct spoe_agent  *agent = SPOE_APPCTX(appctx)->agent;
 	char *frame, *buf;
 	int   ret;
@@ -1834,7 +1834,7 @@
 static int
 spoe_handle_disconnecting_appctx(struct appctx *appctx)
 {
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 	char  *frame;
 	int    ret;
 
@@ -1899,7 +1899,7 @@
 static void
 spoe_handle_appctx(struct appctx *appctx)
 {
-	struct conn_stream *cs = appctx->owner;
+	struct conn_stream *cs = appctx_cs(appctx);
 	struct spoe_agent  *agent;
 
 	if (SPOE_APPCTX(appctx) == NULL)