BUG/MINOR: cli: fix server name output in "show fd"

A server name was displayed as <srv>/<proxy> instead of the reverse.
It only confuses diagnostics. This was introduced by commit 7a4a0ac71
("MINOR: cli: add a new "show fd" command") so this fix can be backport
down to 1.8.
diff --git a/src/cli.c b/src/cli.c
index bc561cf..b313219 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -1280,7 +1280,7 @@
 			if (px)
 				chunk_appendf(&trash, " px=%s", px->id);
 			else if (sv)
-				chunk_appendf(&trash, " sv=%s/%s", sv->id, sv->proxy->id);
+				chunk_appendf(&trash, " sv=%s/%s", sv->proxy->id, sv->id);
 			else if (li)
 				chunk_appendf(&trash, " fe=%s", li->bind_conf->frontend->id);