Allow blocked XREAD on a cluster replica (#7881)

I suppose that it was overlooked, since till recently none of the blocked commands were readonly.

other changes:
- add test for the above.
- add better support for additional (and deferring) clients for
  cluster tests
- improve a test which left the client in MULTI state.

1 files changed, 13 insertions, 0 deletions

diff --git a/tests/instances.tcl b/tests/instances.tcl
index 5c4b665db..d3b1b50cd 100644
--- a/tests/instances.tcl
+++ b/tests/instances.tcl
@@ -606,3 +606,16 @@ proc restart_instance {type id} {
     }
 }
 
+proc redis_deferring_client {type id} {
+    set port [get_instance_attrib $type $id port]
+    set host [get_instance_attrib $type $id host]
+    set client [redis $host $port 1 $::tls]
+    return $client
+}
+
+proc redis_client {type id} {
+    set port [get_instance_attrib $type $id port]
+    set host [get_instance_attrib $type $id host]
+    set client [redis $host $port 0 $::tls]
+    return $client
+}