Assertion `!check_buffer || (vio_pending(net->vio) <= 1)' failed in net_clear() when a PS statement is executed after a BF abort

[philip-galera]

If a transaction is BF-aborted, subsequent PS statement will either cause the client to assert:

mysqltest: /home/philips/git/mysql-wsrep/sql/net_serv.cc:200: void net_clear(NET*, my_bool): Assertion `!check_buffer || (vio_pending(net->vio) <= 1)' failed.

or fail to return a result set.

To reproduce:

perl mysql-test-run.pl --suite galera galera_bf_abort --ps-protocol

[philip-galera]

Still reproducible as of today.

[philip-galera]

Fix pushed.