MINOR: ring: re-work ring attach generic API.

Attach is now independent on appctx, which was unused anyway.
diff --git a/include/proto/ring.h b/include/proto/ring.h
index d927b38..8adbb9c 100644
--- a/include/proto/ring.h
+++ b/include/proto/ring.h
@@ -30,7 +30,7 @@
 struct ring *ring_resize(struct ring *ring, size_t size);
 void ring_free(struct ring *ring);
 ssize_t ring_write(struct ring *ring, size_t maxlen, const struct ist pfx[], size_t npfx, const struct ist msg[], size_t nmsg);
-int ring_attach_appctx(struct ring *ring, struct appctx *appctx);
+int ring_attach(struct ring *ring);
 void ring_detach_appctx(struct ring *ring, struct appctx *appctx, size_t ofs);
 int ring_attach_cli(struct ring *ring, struct appctx *appctx);
 int cli_io_handler_show_ring(struct appctx *appctx);
diff --git a/src/ring.c b/src/ring.c
index b6fc4c1..2a6bb02 100644
--- a/src/ring.c
+++ b/src/ring.c
@@ -206,7 +206,7 @@
  * already attached. On success, the caller MUST call ring_detach_appctx()
  * to detach itself, even if it was never woken up.
  */
-int ring_attach_appctx(struct ring *ring, struct appctx *appctx)
+int ring_attach(struct ring *ring)
 {
 	int users = ring->readers_count;
 
@@ -245,7 +245,7 @@
  */
 int ring_attach_cli(struct ring *ring, struct appctx *appctx)
 {
-	if (!ring_attach_appctx(ring, appctx))
+	if (!ring_attach(ring))
 		return cli_err(appctx,
 		               "Sorry, too many watchers (255) on this ring buffer. "
 		               "What could it have so interesting to attract so many watchers ?");