Assertion `!check_buffer || (vio_pending(net->vio) <= 1)' failed in net_clear() during disconnect with PS protocol

[sciascid]

The assertion can be reproduced with the following test:

--source include/galera_cluster.inc

if (`SELECT $PS_PROTOCOL = 0`)
{
  --skip Test requires: ps-protocol enabled
}

--connection node_1
CREATE TABLE t1 (f1 INTEGER PRIMARY KEY);

# Creates a prepared stmt
INSERT INTO t1 VALUES(1); 

START TRANSACTION;
# Notice that using --send here causes mysqltest
# to fallback to normal protocol
--send INSERT INTO t1 VALUES(2); 

--connection node_2
INSERT INTO t1 VALUES(2);
DROP TABLE t1;

The assertion appears in mysqltest client, when disconnecting and ongoing transaction at the end of the test. For assertion to trigger, there needs to be a prepared statement prior, and followed by a BF aborted transaction.